Carrier GAS FURNACE 58MXA Installation and user guide

58MXA
4-Way Multipoise Fixed-Capacity
Direct-Vent Condensing Gas Furnace
Service and Maintenance Instructions
→For Sizes 040—140, Series 130
NOTE: Read the entire instruction manual before performing any
service or maintenance.
This symbol →indicates a change since the last issue.
Index Page
SAFETY CONSIDERATIONS..................................................1-2
ELECTROSTATIC DISCHARGE (ESD) PRECAUTIONS........2
GENERAL......................................................................................2
CARE AND MAINTENANCE................................................2-11
Cleaning and/or Replacing Air Filter.......................................3
Blower Motor and Wheel Maintenance................................3-4
Cleaning Burners...................................................................4-5
Cleaning Heat Exchangers....................................................5-7
Primary Heat Exchangers ................................................5-7
Secondary Heat Exchangers................................................7
Flushing Collector Box and Drainage System ........................7
Servicing Hot Surface Ignitor...............................................7-8
Electrical Controls and Wiring.................................................8
Troubleshooting................................................................8-9-10
Checking Heat Tape Operation (If Applicable) ....................10
Winterizing ........................................................................10-11
WIRING DIAGRAM...................................................................12
SERVICE LABEL .......................................................................13
TROUBLESHOOTING GUIDE............................................14-15
SAFETY CONSIDERATIONS
Installing and servicing heating equipment can be hazardous due to
gas and electrical components. Only trained and qualified person-
nel should install, repair, or service heating equipment.
Untrained personnel can perform basic maintenance functions
such as cleaning and replacing air filters. All other operations must
be performed by trained service personnel. When working on
heating equipment, observe precautions in the literature, on tags,
and on labels attached to or shipped with the unit and other safety
precautions that may apply.
Follow all safety codes. In the United States, follow all safety
codes including the National Fuel Gas Code (NFGC) NFPA
54-1996/ANSI Z223.1-1996 and the Installation Standards, Warm
Air Heating and Air Conditioning Systems (NFPA 90B)
ANSI/NFPA 90B. In Canada, refer to the CAN/CGA-B149.1- and
.2-M95 National Standard of Canada, Natural Gas and Propane
Installation Codes (NSCNGPIC). Wear safety glasses and work
gloves. Have a fire extinguisher available during start-up and
adjustment procedures and service calls.
Recognize safety information. This is the safety-alert symbol .
When you see this symbol on the unit and in instructions or
manuals, be alert to the potential for personal injury.
Understand the signal words DANGER, WARNING, and CAU-
TION. These words are used with the safety-alert symbol. DAN-
GER identifies the most serious hazards which will result in severe
personal injury or death. WARNING signifies hazards which
could result in personal injury or death. CAUTION is used to
identify unsafe practices which would result in minor personal
injury or product and property damage. NOTE is used to highlight
suggestions which will result in enhanced installation, reliability,
or operation.
A93040
®
ama
CANADIAN GAS ASSOCIATION
APPROVED
R
As an ENERGY STAR®
Partner, Carrier Corporation
has determined that this prod-
uct meets the ENERGY
STAR® guidelines for energy
efficiency.
®
• • • • • • • • • • • • • • •
ULTRA HIGH EFFICIENCY
GAS FURNANCE
®
A93007
REGISTERED QUALITY SYSTEM
Fig. 1—Multipoise Furnace in Upflow Orientation
Visit www.carrier.com
Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.
Book 1 4
Tab 6a 8a PC 101 Catalog No. 535-745 Printed in U.S.A. Form 58MXA-6SM Pg 1 5-99 Replaces: 58MXA-5SM

The ability to properly perform maintenance on this equip-
ment requires certain expertise, mechanical skills, tools, and
equipment. If you do not possess these, do not attempt to
perform any maintenance on this equipment other than those
procedures recommended in the User’s Manual. FAILURE
TO FOLLOW THIS WARNING COULD RESULT IN
POSSIBLE DAMAGE TO THIS EQUIPMENT, SERIOUS
PERSONAL INJURY, OR DEATH.
Never store anything on, near, or in contact with the furnace,
such as:
1. Spray or aerosol cans, rags, brooms, dust mops, vacuum
cleaners, or other cleaning tools.
2. Soap powders, bleaches, waxes or other cleaning com-
pounds, plastic or plastic containers, gasoline, kerosene,
cigarette lighter fluid, dry cleaning fluids, or other volatile
fluids.
3. Paint thinners and other painting compounds, paper bags,
or other paper products.
Failure to follow this warning can cause corrosion of the heat
exchanger, fire, personal injury, or death.
ELECTROSTATIC DISCHARGE (ESD) PRECAUTIONS
Electrostatic discharge can affect electronic components.
Take precautions during furnace installation and servicing to
protect the furnace electronic control. Precautions will pre-
vent electrostatic discharges from personnel and hand tools
which are held during the procedure. These precautions will
help to avoid exposing the control to electrostatic discharge
by putting the furnace, the control, and the person at the same
electrostatic potential.
1. Disconnect all power to the furnace. DO NOT TOUCH THE
CONTROL OR ANY WIRE CONNECTED TO THE CON-
TROL PRIOR TO DISCHARGING YOUR BODY’S ELEC-
TROSTATIC CHARGE TO GROUND.
2. Firmly touch a clean, unpainted, metal surface of the furnace
chassis which is close to the control. Tools held in a person’s
hand during grounding will be satisfactorily discharged.
3. After touching the chassis you may proceed to service the
control or connecting wires as long as you do nothing that
recharges your body with static electricity (for example; DO
NOT move or shuffle your feet, DO NOT touch ungrounded
objects, etc.).
4. If you touch ungrounded objects (recharge your body with
static electricity), firmly touch furnace again before touching
control or wires.
5. Use this procedure for installed and uninstalled (ungrounded)
furnaces.
6. Before removing a new control from its container, discharge
your body’s electrostatic charge to ground to protect the
control from damage. If the control is to be installed in a
furnace, follow items 1 through 5 before bringing the control
or yourself into contact with the furnace. Put all used AND
new controls into containers before touching ungrounded
objects.
7. An ESD service kit (available from commercial sources) may
also be used to prevent ESD damage.
GENERAL
These instructions are written as if the furnace is installed in an
upflow application. An upflow furnace application is where the
blower is located below the combustion and controls section of the
furnace, and conditioned air is discharged upward. Since this
furnace can be installed in any of the 4 positions shown in Fig. 2,
you may need to revise your orientation to component location
accordingly.
CARE AND MAINTENANCE
For continuing high performance and to minimize possible equip-
ment failure, it is essential that maintenance be performed annually
on this equipment. Consult your local dealer for maintenance and
maintenance contract availability.
Turn off the gas and electrical supplies to the unit before
performing any maintenance or service. Follow the operating
instructions on the label attached to the furnace. Failure to
follow this warning could result in personal injury or death.
The minimum maintenance that should be performed on this
equipment is as follows:
1. Check and clean or replace air filter each month as required.
2. Check blower motor and wheel for cleanliness annually.
3. Check electrical connections for tightness and controls for
proper operation each heating season. Service as necessary.
4. Check for proper condensate drainage. Clean as necessary.
5. Check for blockages in combustion-air and vent pipes annu-
ally.
6. Check burners for cleanliness annually.
Personal injury could result from sharp metal edges, etc. Use
care when removing parts.
Fig. 2—Multipoise Orientations A93041
UPFLOW
DOWNFLOW
HORIZONTAL
LEFT
AIRFLOW AIRFLOW
AIRFLOW
AIRFLOW
HORIZONTAL
RIGHT
2

Step 1—Cleaning and/or Replacing Air Filter
The air filter arrangement may vary depending on the application
or orientation.
Never operate unit without a filter or with the blower access
panel removed. Failure to follow this warning could result in
a fire or personal injury.
To clean or replace the filters, proceed as follows:
1. Turn off electrical supply to furnace.
2. Remove main furnace door and blower access panel.
3. Release filter retainer wire. (See Fig. 3 and 4.)
4. Slide filter out of furnace.
5. Furnaces are equipped with permanent, washable filter(s).
Clean filter by spraying cold tap water through filter in
opposite direction of airflow.
6. Rinse filter and let dry. Oiling or coating of filter is not
recommended.
7. Place filter in furnace.
8. Replace blower access panel and main furnace door.
9. Turn on electrical supply to furnace.
NOTE: If the filter has cross-mesh binding, the binding must face
the blower. If the filter has an air direction arrow, the arrow must
point toward the blower.
Step 2—Blower Motor and Wheel Maintenance
To ensure long life, economy, and high efficiency, clean accumu-
lated dirt and grease from blower wheel and motor annually.
The inducer and blower motors are pre-lubricated and require no
additional lubrication. These motors can be identified by the
absence of oil ports on each end of the motor.
The following items should be performed by a qualified service
technician.
Clean blower motor and wheel as follows:
1. Turn off electrical supply to furnace.
2. Remove main furnace door and blower access panel.
3. Disconnect wires.
All factory wires can be left connected, but field thermostat
connections may need to be disconnected depending on their
length and routing.
4. Position control box, transformer, and door switch assembly to
right side of furnace casing.
5. If condensate trap is located in left- or right-hand side of
furnace casing, proceed to item 6, otherwise remove trap and
tubing as described below.
a. Disconnect field drain connection from condensate trap.
b. Disconnect drain and relief port tubes from condensate
trap.
c. Remove condensate trap from blower shelf.
6. Remove screws securing blower assembly to blower shelf and
slide blower assembly out of furnace.
7. Clean blower wheel and motor by using a vacuum with soft
brush attachment. Be careful not to disturb balance weights
(clips) on blower wheel vanes. Do not bend wheel or blades as
balance will be affected.
8. If greasy residue is present on blower wheel, remove wheel
from the blower housing and wash it with an appropriate
degreaser. To remove wheel:
a. Mark blower wheel location on shaft before disassembly to
ensure proper reassembly.
b. Loosen setscrew holding blower wheel on motor shaft.
NOTE: Mark blower mounting arms and blower housing so each
arm is positioned at the same hole location during reassembly.
c. Mark blower wheel orientation and cutoff plate location to
ensure proper reassembly.
d. Remove screws securing cutoff plate and remove cutoff
plate from housing.
e. Remove bolts holding motor mounts to blower housing and
slide motor and mounts out of housing. Disconnect capaci-
tor and ground wire attached to blower housing before
removing motor.
f. Remove blower wheel from housing.
g. Clean wheel per instructions on degreaser cleaner.
9. Reassemble motor and blower wheel by reversing items 8b
through 8f. Ensure wheel is positioned for proper rotation. Be
sure to reattach ground wire.
10. Reinstall blower assembly in furnace.
Fig. 3—Bottom Filter Arrangement A93046
WASHABLE
FILTER
FILTER
SUPPORT FILTER
RETAINER
Fig. 4—Filter Installed for Side Inlet A93045
FILTER
RETAINER
WASHABLE
FILTER
3

11. Reinstall condensate trap and tubing if previously removed.
a. Reinstall condensate trap in hole in blower shelf.
b. Connect condensate trap drain tubes. See Fig. 8 or tubing
diagram on main furnace door for proper tube location.
(1.) Connect 1 tube (blue or blue and white striped) from
collector box.
(2.) Connect 1 tube (violet or unmarked) from inducer
housing.
(3.) Connect 1 tube (relief port, green or pink) from
collector box.
c. Connect field drain to condensate trap.
NOTE: Ensure tubes are not kinked or pinched, as this will affect
operation.
12. Reinstall control box, transformer, and door switch assembly
on blower shelf.
13. Reconnect wires.
Refer to furnace wiring diagram, and connect thermostat leads
if previously disconnected. (See Fig. 15.)
NOTE: Refer to Table 1 for motor speed lead relocation if leads
were not identified before disconnection.
Heating speed selection MUST be adjusted to provide proper
temperature rise as specified on the rating plate. Failure to
adjust the heating speed may shorten heat exchanger life.
14. Turn on electrical supply. Manually close blower access panel
door switch. Use a piece of tape to hold switch closed. Check
for proper rotation and speed changes between heating and
cooling by jumpering R to G and R to Y on control center
thermostat terminals. (See Fig. 12.)
Blower access panel door switch opens 115-v power to
control center. No component operation can occur. Caution
must be taken when manually closing this switch for service
purposes. Failure to follow this warning could result in
personal injury or death.
15. If furnace is operating properly, release blower access panel
door switch, replace blower access panel, and replace main
furnace door.
Step 3—Cleaning Burners
The following items should be performed by a qualified service
technician. If the burners develop an accumulation of light dirt or
dust, they may be cleaned by using the following procedure:
1. Turn off gas and electrical supplies to furnace.
2. Remove main furnace door.
3. Remove burner box cover.
4. Using backup wrench, disconnect gas supply pipe from gas
valve.
5. Remove wires from gas valve. Note location for reassembly.
Label all wires prior to disconnection when servicing con-
trols. Wiring errors can cause improper and dangerous
operation.
6. Remove burner box pressure tube from gas valve regulator
fitting.
7. Remove screws that secure manifold to burner box. (See Fig.
5.)
8. Remove manifold, orifices, and gas valve as 1 assembly.
9. Remove screws attaching burner assembly in burner box.
10. Remove burner assembly from burner box.
NOTE: All burners are attached to burner bracket and can be
removed as 1 assembly.
11. Clean burners with soft brush and vacuum.
12. Reinstall manifold, orifice, and gas valve assembly in burner
box. Ensure manifold seal grommet is installed properly and
burners fit over orifices.
13. Reconnect wires to gas valve. Refer to furnace wiring diagram
for proper wire location.
14. Reinstall burner box pressure tube to gas valve regulator
fitting.
15. Reinstall gas supply pipe to gas valve using backup wrench on
gas valve to prevent rotation and improper orientation.
NOTE: Use propane gas resistant pipe dope to prevent gas leaks.
DO NOT use Teflon tape.
Gas valve switch or knob MUST be facing forward or tilted
upward. Failure to follow this warning could result in
property damage, personal injury, or death.
16. Replace burner box cover.
17. Turn on gas and electrical supplies to furnace.
18. Check for gas leaks.
Table 1—Speed Selector
COLOR SPEED FACTORY
ATTACHED TO
Black High Cool
Yellow (When Present) Medium High Spare
Blue Medium Low Heat
Red Low Spare
White Common Com
Fig. 5—Burner Box Assembly A93295
MANIFOLD
MOUNTING
SCREW
MANIFOLD
GAS VALVE
REGULATOR
FITTING
GAS VALVE
4

Never use matches, candles, flame, or other sources of
ignition to check for gas leakage. Use a soap-and-water
solution. Failure to follow this warning could result in a fire,
personal injury, or death.
19. Replace main furnace door.
Step 4—Cleaning Heat Exchangers
The following items should be performed by a qualified service
technician.
PRIMARY HEAT EXCHANGERS
If the heat exchangers get an accumulation of light dirt or dust on
the inside, they may be cleaned by the following procedure:
NOTE: If the heat exchangers get a heavy accumulation of soot
and carbon, both the primary and secondary heat exchangers
should be replaced rather than trying to clean them thoroughly due
to their intricate design. A build-up of soot and carbon indicates
that a problem exists which needs to be corrected, such as
improper adjustment of manifold pressure, insufficient or poor
quality combustion air, improper vent termination, incorrect size
or damaged manifold orifice(s), improper gas, or a restricted heat
exchanger (primary or secondary). Action must be taken to correct
the problem.
1. Turn off gas and electrical supplies to furnace.
2. Remove main furnace door.
3. Disconnect wires or connectors to rollout switch, gas valve,
ignitor, and flame sensor.
Label all wires prior to disconnection when servicing con-
trols. Wiring errors can cause improper and dangerous
operation.
4. Disconnect combustion-air intake pipe from intake housing.
5. Remove the pressure switch tube from intake housing.
6. Remove screws attaching intake housing to burner box, and
rotate intake housing away from burner box for removal.
7. Using backup wrench, disconnect gas supply pipe from gas
valve.
8. Disconnect pressure tubing from gas valve.
9. Remove 2 screws attaching top filler panel and rotate upwards
to gain access to screws attaching burner box to cell panel.
10. Remove screws attaching burner box to cell panel. (See Fig.
5.)
NOTE: Burner box cover, manifold, gas valve, and burner
assembly should be removed as 1 assembly.
11. Clean heat exchanger openings with a vacuum and a soft
brush. (See Fig. 6.)
NOTE: After cleaning, inspect the heat exchangers to ensure they
are free of all foreign objects that may restrict flow of combustion
products.
12. Reverse items 4 through 10 for reassembly.
The ground wire from the gas valve MUST be attached to the
burner box attachment screw. Failure to attach this ground
wire to an adequate casing ground will cause the furnace
control to lock out.
NOTE: Be sure burner box gasket is installed between burner box
and cell panel. If gasket is damaged, replace it.
NOTE: Inspect combustion-air intake housing. If foamed gasket
was removed, check for any damage. If gasket is damaged in any
way, it must be repaired. To repair, remove damaged gasket
section, apply sealant releasing agent such as PAM cooking spray
or equivalent (must not contain corn or canola oil, aromatic or
halogenated hydrocarbons or inadequate seal may occur) to burner
box and apply a small bead of G.E. RTV 162. G.E. RTV 6702, or
Dow-Corning RTV 738 sealant to edge of combustion-air intake
housing. (See Fig. 7.)
13. Refer to furnace wiring diagram and reconnect wires to rollout
switch, gas valve, ignitor, and flame sensor.
14. Reconnect pressure switch tubes to gas valve and intake
housing. Refer to tube routing label on main furnace door for
proper tube location. Be sure tubes are not kinked. (See Fig.
8.)
15. Turn on gas and electrical supplies to furnace.
16. Check furnace operation through 2 complete heat operating
cycles. Look through sight glass in burner enclosure to check
burners. Burner flames should be clear blue, almost transpar-
ent. (See Fig. 9.)
17. Check for gas leaks.
Fig. 6—Cleaning Inlet Openings of Primary Heat
Exchangers
A93080
PRIMARY HX
INLET OPENINGS
Fig. 7—Combustion-Air Intake Housing Gasket
Repair
A93087
PAM
RTV
5

Never use matches, candles, flame, or other sources of
ignition to check for gas leakage. Use a soap-and-water
solution. Failure to follow this warning could result in a fire,
personal injury, or death.
18. Replace main furnace door.
SECONDARY HEAT EXCHANGERS
NOTE: The condensing side (inside) of the secondary heat
exchangers CANNOT be serviced or inspected. A small number of
bottom outlet openings can be inspected by removing the inducer
assembly. See Flushing Collector Box and Drainage System
section for details on removing inducer assembly.
Step 5—Flushing Collector Box and Drainage
System
1. Turn off gas and electrical supplies to furnace.
2. Remove main furnace door.
3. Disconnect inducer motor and pressure switch wires or
connectors.
→Fig. 8—Furnace Pressure and Drain Tubing Diagram A99102
Furnace is shipped from factory in upflow configuration. Pressure tube and drain tube routing MUST match the diagrams below.
Tube location when used in DOWNFLOW application
Tube location when used on
HORIZONTAL - RIGHT application
PLUG
CAP
COLLECTOR BOX DRAIN TUBE
(BLUE & WHITE STRIPED)
COLLECTOR BOX TUBE
(PINK)
COLLECTOR BOX DRAIN TUBE
(BLUE)
INDUCER HOUSING DRAIN TUBE
(VIOLET)
COLLECTOR BOX TUBE
(PINK)
COLLECTOR BOX DRAIN
TUBE
(BLUE & WHITE STRIPED)
COLLECTOR BOX DRAIN TUBE
(BLUE)
INDUCER HOUSING (MOLDED) DRAIN TUBE
(BEHIND COLLECTOR BOX DRAIN TUBE)
FIELD-INSTALLED
FACTORY-SUPPLIED DRAIN TUBE
COUPLING (LEFT DRAIN OPTION)
FIELD-INSTALLED FACTORY-SUPPLIED
DRAIN TUBE
FIELD-INSTALLED
FACTORY-SUPPLIED 1/2-IN.
CPVC STREET ELBOWS (2)
FORLEFTDRAINOPTION
COLLECTOR BOX TUBE
(GREEN)
CONDENSATE TRAP
CAP
Condensate Trap; Factory Installed
in Blower Shelf
CONDENSATE TRAP
COLLECTOR BOX TUBE(GREEN)
Condensate Trap on LEFT
Side Optional
CAP PLUG
COLLECTOR BOX
DRAIN TUBE (BLUE)
PLUGGED END
COLLECTOR BOX DRAIN TUBE
(BLUE & WHITE STRIPED)
COLLECTOR BOX
TUBE (GREEN)
COLLECTOR BOX
TUBE (PINK)
COLLECTOR BOX
EXTENSION TUBE
CONDENSATE TRAP
INDUCER HOUSING DRAIN TUBE (VIOLET)
COLLECTOR BOX
EXTENSION TUBE
COLLECTOR BOX TUBE
(PINK)
COLLECTOR BOX DRAIN TUBE
(BLUE)
COLLECTOR BOX TUBE
(GREEN)
CONDENSATE TRAP
INDUCER HOUSING DRAIN
TUBE (VIOLET) COLLECTOR BOX EXTENSION TUBE
COLLECTOR BOX DRAIN
TUBE
(BLUE & WHITE STRIPED)
Condensate Trap on
RIGHT Side
COLLECTOR BOX
EXTENSION DRAIN TUBE
DRAIN TUBE COUPLING
GAS VALVE
DRAIN TUBES ROUTED IN
FRONT OF GAS VALVE
AUXILIARY "J" BOX RELOCATED HERE
PLUG
CAP
COLLECTOR BOX DRAIN TUBE
(BLUE & WHITE STRIPED)
CONDENSATE TRAP
COLLECTOR BOX
EXTENSION TUBE
COLLECTOR BOX
TUBE (GREEN)
INDUCER HOUSING
DRAIN TUBE
(VIOLET)
COLLECTOR BOXTUBE (PINK)
RELOCATE TUBE BETWEEN BLOWER
SHELF AND INDUCER HOUSING FOR
040,060, AND 080 HEATING INPUT
FURNACES
CAP
PLUG
COLLECTOR BOX DRAIN TUBE
(BLUE) COLLECTOR BOX EXTENSION TUBE
COLLECTOR BOX TUBE (PINK)
COLLECTOR BOX
TUBE (GREEN)
COLLECTOR BOX DRAIN TUBE
(BLUE AND WHITE STRIPED) INDUCER HOUSING DRAIN TUBE (VIOLET)
CONDENSATE TRAP
Condensate Trap on
LEFT Side
COLLECTOR BOX
DRAIN TUBE (BLUE)
PLUG
Tube location when used in UPFLOW application
Tube location when used on
HORIZONTAL - LEFT application
CAP
PLUG
COLLECTOR BOX
EXTENSION TUBE
DRAIN TUBE
COUPLING
COLLECTOR BOX EXTENSION DRAIN TUBE
(Blower access panel removed)
1. All tubing must be connected securely and routed to avoid kinks and traps.
2. Pressure tubing must always slope away from pressure switch to collector box connection as shown.
3. HORIZONTAL-LEFT installations require the collector box pressure tube to be relocated between the inducer housing and the blower shelf to
prevent a trap.Refer to the Installation Instructions for further details.
NOTE:
324999-201 REV. A
(LIT. BOTTOM)
FIELD-INSTALLED
FACTORY-SUPPLIED
DRAIN TUBE COUPLING
(RIGHT DRAIN OPTION)
BURNER ENCLOSURE
PRESSURE REFERENCE
TUBE ASSEMBLY
BURNER ENCLOSURE
PRESSURE REFERENCE
TUBE ASSEMBLY
BURNER ENCLOSUREPRESSURE
REFERENCE TUBE ASSEMBLY
BURNER ENCLOSURE
PRESSURE REFERENCE
TUBE ASSEMBLY
BURNER ENCLOSURE
PRESSURE REFERENCE
TUBE ASSEMBLY
BURNER ENCLOSUREPRESSURE
REFERENCE TUBE ASSEMBLY
TUBE ROUTING
Fig. 9—Burner Flame A89020


BURNER FLAME
BURNER
MANIFOLD
6

4. Disconnect pressure switch tubes.
5. Disconnect vent pipe from inducer housing outlet by loosen-
ing coupling clamp on inducer outlet.
6. Disconnect drain tube from inducer housing. (See Fig. 8.)
7. Remove inducer housing assembly by removing 4 bolts
attaching assembly to cell panel.
8. Flush inside of collector box with water until discharge from
condensate trap is clean and runs freely.
NOTE: Ensure the drain tube disconnected from the inducer
housing is higher than the collector box opening or water will flow
out tube.
9. Inspect inside area of collector box for any pieces of foreign
materials and remove if present.
DO NOT use wire brush or other sharp object to inspect or
dislodge materials in secondary heat exchangers as failure of
the secondary heat exchanger will occur. Flush with water
only.
10. Reassemble inducer assembly by reversing items 5 through 7.
Tighten the vent coupling clamp screw(s) to 15 in.-lb. of
torque.
NOTE: If seal between the inducer housing and the collector box
is damaged in any way, it must be repaired. To repair, apply
sealant releasing agent such as PAM cooking spray or equivalent
(must not contain corn or canola oil, aromatic or halogenated
hydrocarbons or inadequate seal may occur) to inducer housing.
(See Fig. 10.) Apply a small bead of G.E. RTV 162, G.E. RTV
6702, or Dow-Corning RTV 738 sealant to groove in collector
box.
11. Refer to furnace wiring diagram and reconnect wires to
inducer motor and pressure switch or connectors.
12. Reconnect pressure tubes to pressure switch. See diagram on
main furnace door for proper location of tubes. Be sure tubes
are not kinked. (See Fig. 8.)
13. Turn on gas and electrical supplies to furnace.
14. Check furnace operation through 2 complete heat operating
cycles. Check area below inducer housing, vent pipe, and
condensate trap to ensure no condensate leaks occur. If leaks
are found, correct the problem.
15. Check for gas leaks.
Never use matches, candles, flame, or other sources of
ignition to check for gas leakage. Use a soap-and-water
solution. Failure to follow this warning could result in a fire,
personal injury, or death.
16. Replace main furnace door.
Step 6—Servicing Hot Surface Ignitor
The ignitor does NOT require annual inspection. Check ignitor
resistance before removal.
1. Turn off gas and electrical supplies to furnace.
2. Remove main furnace door.
3. Disconnect ignitor wire connection.
4. Check ignitor resistance.
a. Using an ohm meter, check resistance across both ignitor
leads in connector.
b. Cold reading should be between 45 ohms and 90 ohms.
c. If ohm reading is higher than 110 ohms, ignitor is cracked
and must be replaced.
5. Remove ignitor assembly.
Allow ignitor to cool before removal. Normal operation
temperatures exceed 2000°F.
a. Do not remove ignitor from bracket while assembly is in
furnace. Using a 1/4 in. nutdriver, remove screw securing
bracket and ignitor assembly to bottom of burner box. The
screw in the bracket is always located toward outside of
burner box. The screw may be hidden by inlet box or inlet
pipe, but can be removed without removing either. After
removing screw, slide ignitor and bracket toward outside of
burner box and pull straight out.
The ignitor is fragile. DO NOT allow it to hit the side of the
burner box opening while removing or replacing it.
b. Inspect ignitor for a white area indicating a crack may be
present. If found, replace ignitor.
NOTE: A small crack cannot be seen on a new ignitor. After a
period of operation, a white area will be visible around the crack.
c. If replacement is required, replace ignitor on ignitor bracket
external to furnace to avoid damage as the silicon portion is
very brittle and will easily crack or shatter.
d. To remove ignitor from ignitor bracket, remove screw
holding ignitor ceramic block to bracket and pull ceramic
block out of bracket.
6. To replace ignitor/ignitor assembly, reverse items 5a through
5d.
7. Reconnect ignitor wire connection.
8. Turn on gas and electrical supplies to furnace.
9. Verify ignitor operation by initiating control board self-test
feature or by cycling thermostat.
Fig. 10—Gasket on Collector Box A93081
RTV
PAM
7
→
→

10. Replace main furnace door.
Step 7—Electrical Controls and Wiring
There may be more than 1 electrical supply to the unit. Check
accessories and cooling unit for additional electrical supplies.
The electrical ground and polarity for 115-v wiring must be
maintained properly. Refer to Fig. 11 for field wiring information
and to Fig. 15 for unit wiring information.
NOTE: If the polarity is not correct, the STATUS LED on the
control center will flash rapidly and prevent the furnace from
operating. The control system also requires an earth ground for
proper operation of the control center and flame sensing.
The 24-v circuit contains an automotive-type, 3-amp fuse located
on the control center. (See Fig. 12.) Any direct shorts of the 24-v
wiring during installation, service, or maintenance will cause this
fuse to blow. If fuse replacement is required, use ONLY a fuse of
identical size.
With power to the unit disconnected, check all electrical connec-
tions for tightness. Tighten all screws on electrical connections. If
any smoky or burned connections are found, disassemble the
connection, clean all parts, strip wire, and reassemble properly and
securely.
Reconnect electrical supply to unit and observe unit through 1
complete operating cycle. Electrical controls are difficult to check
without proper instrumentation; if there are any discrepancies in
the operating cycle, contact your dealer and request service.
Step 8—Troubleshooting
For an explanation of status codes, refer to service label located on
back of main furnace door or Fig. 16, and the Troubleshooting
Guide.
The control center stores 1 status code (representing the last fault
to occur) for a period of 48 hr or until the 115- or 24-v power is
interrupted.
NOTE: Removing blower access panel will open blower access
panel door switch and terminate 115-v power to control center.
The status code will be erased. Look into blower access panel sight
glass for current LED status BEFORE removing blower access
panel.
The unit’s component test is a useful troubleshooting tool since it
displays the current status code of the furnace and functionally
operates all furnace components except the gas valve. The com-
ponent test and methods to initiate it are described below.
COMPONENT TEST SEQUENCE
NOTE: All components are functionally operated except the gas
valve.
When component test is initiated, the following sequence of events
occurs:
1. LED flashes a status code 4 times.
2. Inducer motor starts and continues to run for remainder of
component test.
3. Hot surface ignitor is energized for 15 sec, then de-energized.
4. Main blower operates at cooling speed for 10 sec, then turns
off.
5. Main blower operates at heating speed for 10 sec, then turns
off.
6. Inducer motor stops.
Component test can be initiated by one of the following proce-
dures.
INITIATING COMPONENT TEST AND RETRIEVING STA-
TUS CODE BY REMOVING MAIN LIMIT SWITCH WIRE
NOTE: NO thermostat signal may be present at control center
and all blower time delay off periods must be completed.
Fig. 11—Field Wiring A98325
115-V 
FIELD-SUPPLIED
DISCONNECT
SWITCH

115-V
SINGLE
PHASE
AUXILIARY
J-BOX
FURNACE
CONTROL
CENTER
TWO WIRE
24-V
TERMINAL
BLOCK
THREE-WIRE
HEATING
ONLY
FIVE
WIRE
NOTE 5
NOTE 1
NOTE
3
THERMOSTAT
TERMINALS FIELD-SUPPLIED
DISCONNECT
CONDENSING
UNIT
R
W2

WCR GY
GND
GND
GND
GND
FIELD 24-V WIRING
FIELD 115-, 208/230-, 460-V WIRING
FACTORY 24-V WIRING
FACTORY 115-, 208/230-, 460-V WIRING
208/230- OR
460-V
THREE PHASE
208/230-V
SINGLE
PHASE
W/W1
Y/Y2
G
C
NOTES:
1.
2.
3.
4.
5.
Connect Y or Y/Y2 terminal as shown for proper cooling operation.
Proper polarity must be maintained for 115-v wiring.
Use W2 with 2-stage thermostat when zoning.
If any of the original wire, as supplied, must be replaced, use
same type or equivalent wire.
Some thermostats require a "C" terminal connection as shown.
8

1. Leave 115-v power to furnace turned on.
2. Remove main furnace door.
3. Look into blower access panel sight glass for current LED
status.
NOTE: Leave blower access panel installed to maintain power to
control center to view current LED status.
4. BRIEFLY remove either wire from the main limit switch until
the LED goes out, then reconnect it.
Make sure limit switch wire does not contact any metallic
component such as the gas valve. If wire is shorted, 3-amp
fuse on control center will blow.
NOTE: If wire to main limit is disconnected longer than 4 sec, the
control senses limit circuit is open. Main blower will start and
retrieval request will be ignored.
5. When above items have been completed, the component test
sequence will occur as described in the Component Test
Sequence section above.
NOTE: Be sure to record the status code which is flashed 4 times
at start of component test for further troubleshooting.
6. After component test is completed and LED is ON continu-
ously indicating the furnace is ready to operate when a signal
from the thermostat is received, replace main furnace door.
INITIATING COMPONENT TEST AND RETRIEVING STA-
TUS CODE BY JUMPERING CONTROL TEST TERMINAL
1. Remove main furnace door.
2. Remove blower access panel.
3. Manually close blower access panel door switch. Use a piece
of tape to hold switch closed.
Blower access panel door switch opens 115-v power to
control center. No component operation can occur. Caution
must be taken when manually closing this switch for service
purposes. Failure to follow this warning could result in
electrical shock, personal injury, or death.
4. BRIEFLY short (jumper) TEST, 1/4-in. quick-connect termi-
nal on control center (adjacent to the LED diagnostic light)
and the COM terminal on thermostat connection block. (See
Fig. 12.)
NOTE: If TEST to COM terminals are jumpered longer than 2 sec,
LED will flash rapidly, and retrieval request will be ignored.
5. When above items have been completed, the component test
sequence will occur as described in the Component Test
Sequence section above.
NOTE: Be sure to record the status code which is flashed 4 times
at start of component test for further troubleshooting.
6. After component test is completed and furnace is operating
properly, release blower access panel door switch, replace
blower access panel, and replace main furnace door.
Step 9—Checking Heat Tape Operation (If Applicable)
In applications where the ambient temperature around the furnace
is 32°F or lower, freeze protection measures are required. If this
application is where heat tape has been applied, check to ensure it
will operate when low temperatures are present.
Fig. 12—Control Center A93052
G
R
Y
W
3-AMP FUSE
Com
24V

HUMIDIFIER TERMINAL
(24-VAC 0.5 AMP MAX)
LED OPERATION &
STATUS LIGHT
HARNESS CONNECTOR
24V TRANSFORMER SEC-2
SPARE 1
SPARE 2
EAC 1 (BLACK)
EAC-ELECTRONIC AIR CLEANER
TERMINALS (115-VAC 1.5 AMP MAX)
EAC 2 (WHITE)
115-VAC (L2) NEUTRAL
CONNECTION
24V THERMOSTAT
TERMINALS
BLOWER SPEED
SELECTION TERMINALS
INDUCER MOTOR
CONNECTOR
115-VAC (L1)
POWER
SUPPLY
HOT SURFACE
IGNITOR
CONNECTOR
HEAT
COOL
BLOWER OFF DELAY
ADJUSTMENT SWITCH
SEC-1
TEST/TWIN
HUM
9

NOTE: Heat tape, when used, should be wrapped around the
condensate drain trap and drain line. There is no need to use heat
tape within the furnace casing. Most heat tapes are temperature
activated, and it is not practical to verify the actual heating of the
tape. Check the following:
1. Check for signs of physical damage to heat tape such as nicks,
cuts, abrasions, gnawing by animals, etc.
2. Check for discolored heat tape insulation. If any damage or
discolored insulation is evident, replace heat tape.
3. Check that heat tape power supply circuit is on.
Step 10—Winterizing
Freezing condensate left in the furnace will damage the
equipment.
If the furnace will be off for an extended period of time in a
structure where the temperature will drop to 32°F or below,
winterize as follows:
1. Turn off electrical supply to furnace.
2. Remove main furnace door.
3. Disconnect drain tube from inducer housing. (See Fig. 13.)
4. Insert funnel in drain tube and pour antifreeze, propylene
glycol (RV, swimming pool antifreeze, or equivalent) into
furnace until it is visible at point where condensate enters open
drain. (See Fig. 14.)
5. Reconnect drain tube to inducer housing.
6. Replace main furnace door.
Do not use ethylene glycol (Prestone II antifreeze/coolant or
equivalent automotive type). Failure of plastic components
will occur.
4
→Fig. 13—Inducer Housing Drain Tube A99118 →Fig. 14—Funnel in Drain and Antifreeze Running
Through Trap
A99119
If this furnace is installed in an unconditioned space where
the ambient temperatures may be 32°F or lower, freeze
protection measures must be taken.
A93058
32°F MINIMUM INSTALLED
AMBIENT OR FREEZE
PROTECTION REQUIRED
10

PCB
BLOWER OFF DELAY
SELECTION CHART
90 SEC
135 SEC
180 SEC
225 SEC
GVR
HI/LO
RELAY
SEC-1 SEC-2
WHT
PL1 321
654
987
LED
TEST/TWIN
BLOWER
OFF
DELAY
G
R
Y
W
C
HUM
HSIR IDR BLWR
BLOWER
SPEED
SELECT
FU1
COOL
HEAT
L2
PL3
PL2
VAC
120
L1 PR1 1
2
1
2
3PR2
24 VAC-3A
FUSE
SPARE-2
SPARE-1
EAC-1
EAC-2
C
1.5 AMP
12
PL5 WHT BRN
GRN
BLK
IDM
BRN
CAP -2
WHT
WHT
BLK BLK
HSI
AUX
OL
M
BLK
WHT
WHT (COM)
RED (LO)
BLU (MED LO)
NOTE #8
OL
START
BLWM
YEL (MED HI)
BLK (HI)
BRN
BRN
TRAN
BLU
RED
BLK
WHT
WHT (COM)
GRN
CAP -1
GRN 2-C
RED
FSE
NOTE #5
1-M 3-P
GV
FRS
BLU YEL
RED
NOTE #6
LS
RED
ORN
PRS (WHEN USED)
LGPS
FUSED DISCONNECT
SWITCH (WHEN REQ'D)
NOTE #4
WHT
GRN
GRN
JB
LEGEND
BLWR BLOWER MOTOR RELAY, SPST-(N.O.)
BLWM BLOWER MOTOR
CAP CAPACITOR
CPU MICROPROCESSOR AND CIRCUITRY
EAC-1 ELECTRONIC AIR CLEANER CONNECTION (115 VAC 1.5 AMP MAX.)
EAC-2 ELECTRONIC AIR CLEANER CONNECTION (COMMON)
FRS FLAME ROLLOUT SW. -MANUAL RESET, SPST-(N.C.)
FSE FLAME PROVING ELECTRODE
FU1 FUSE, 3 AMP, AUTOMOTIVE BLADE TYPE, FACTORY INSTALLED
FU2 FUSE OR CIRCUIT BREAKER CURRENT INTERRUPT DEVICE
(FIELD INSTALLED & SUPPLIED)
GND EQUIPMENT GROUND
GV GAS VALVE-REDUNDANT OPERATORS
GVR GAS VALVE RELAY, DPST-(N.O.)
HI/LO BLOWER MOTOR SPEED CHANGE RELAY, SPDT
HSI HOT SURFACE IGNITOR (115 VAC)
HSIR HOT SURFACE IGNITOR RELAY, SPST-(N.O.)
HUM 24VAC HUMIDIFIER CONNECTION (.5 AMP. MAX.)
IDM INDUCED DRAFT MOTOR
IDR INDUCED DRAFT RELAY, SPST-(N.O.)
ILK BLOWER ACCESS PANEL INTERLOCK SWITCH, SPST-(N.O.)
JB JUNCTION BOX
LED LIGHT-EMITTING DIODE FOR STATUS CODES
LGPS LOW GAS PRESSURE SWITCH, SPST-(N.O.)
LS LIMIT SWITCH, AUTO RESET, SPST(N.C.)
OL AUTO-RESET INTERNAL MOTOR OVERLOAD TEMP. SW.
PCB PRINTED CIRCUIT BOARD
PL1 9-CIRCUIT CONNECTOR
PL2 2-CIRCUIT PCB CONNECTOR
PL3 3-CIRCUIT IDM CONNECTOR
PL4 3-CIRCUIT IDM EXTENSION CONNECTOR
PL5 2-CIRCUIT HSI/PCB CONNECTOR
PRS PRESSURE SWITCH, SPST-(N.O.)
SW1 & 2 BLOWER OFF DELAY
TEST/TWIN COMPONENT TEST & TWIN TERMINAL
TRAN TRANSFORMER-115VAC/24VAC
JUNCTION
UNMARKED TERMINAL
PCB TERMINAL
FACTORY WIRING (115VAC)
FACTORY WIRING (24VAC)
FIELD WIRING (115VAC)
FIELD WIRING (24VAC)
CONDUCTOR ON PCB
FIELD WIRING TERMINAL
FIELD EARTH GROUND
EQUIPMENT GROUND
FIELD SPLICE
PLUG RECEPTACLE
L1
L1
BLWR
HI/LO
TO 115VAC FIELD DISCONNECT
NOTE #4
EQUIPMENT GROUND
SPARE-1
HEAT
SPARE-2
COOL NOTE #8
COM
HSIR EAC-1
START
OL
COM
HI
MED HI
MED LO
LO
BLWM
SCHEMATIC DIAGRAM
(NATURAL GAS & PROPANE)
EAC-2
11HSI
2
PL52
PL2
3PL3
PR2
115VAC
PR1
TRAN 24VAC
1
2
BRN
M
IDR
TEST/TWIN
FU1 NOTE #7
IDM
OL
AUX
BRN
CAP -2
CAP-1
L2
FRS LS
LGPS (WHEN USED)
NOTE #6
PL1 PRS
GV
2-C
1-M
3-P
NOTE #5
8
FSE
9
6
5
CPU
HSIR IDRBLWR
Y
G
C
R
W
GVR-2
SEC-1
HI/LO GVR
GVR-1
SEC-2
NOTES:
322854-101 REV. D (LIT)
1. IF ANY OF THE ORIGINAL EQUIPMENT WIRE IS REPLACED USE WIRE RATED FOR 105˚C.
2. INDUCER (IDM) AND BLOWER (BLWM) MOTORSCONTAIN INTERNAL
AUTO-RESET THERMAL OVERLOAD SWITCHES (OL).
3. BLOWER MOTOR SPEEDSELECTIONSARE FOR AVERAGE CONDITIONS, SEE INSTALLATION
INSTRUCTIONS FOR DETAILS ON OPTIMUM SPEED SELECTION.
4. USE ONLY COPPER WIRE BETWEEN THE DISCONNECT SWITCH AND THE
FURNACE JUNCTION BOX (JB).
5. THIS WIRE MUST BE CONNECTED TO FURNACE SHEETMETAL FOR CONTROL TO PROVE
FLAME.
6. FACTORY CONNECTED WHEN LGPS NOT USED.
7. REPLACE ONLY WITH A 3 AMP FUSE.
8. YELLOW LEAD NOT ON ALL MOTORS.
9. BLOWER-ON DELAY, GAS HEATING 60 SECONDS, COOLING OR HEAT PUMP 2 SECONDS.
10. BLOWER-OFFDELAY,GAS HEATING90, 135, 180 OR 225 SECONDS, COOLINGOR
HEAT PUMP 90 SECONDS. (135 SECONDS ONLY ON SOME MODELS)
11. IGNITION-LOCKOUT WILL OCCUR AFTER FOUR CONSECUTIVE UNSUCCESSFUL
TRIALS-FOR-IGNITION. CONTROL WILL AUTO-RESET AFTER THREEHOURS.
12. SOME MODELS MAY HAVE SPADE QUICK CONNECT TERMINALS.
BLK
OM
SW2
SW1
OM
2
3
4
7
1
OM
HUM
123
WHT
BLK
GRN
PL4
PL4
2
3
1
NEUTRAL
NEUTRAL
WHT
ILK
FU2
BLK
L1
ILK
(NOT ON ALL MODELS)
SEE NOTE #10
NOTE #12
GND
GND
A99106
→Fig. 15—Wiring Diagram
11

→Fig. 16—Service Label A99107
SERVICE
COMPONENT TEST
To initiate the component test sequence,shut OFF the room thermostat or
disconnect the "R" thermostat lead.Briefly short the TEST terminal to the "Com
24V" terminal. Status LED will flash code and then turn ON the inducer motor. The
inducer motor will run for the entire component test. The hot surface ignitor,
blower motor-heat speed, and blower motor-cool speed will be turned ON for
10-15 seconds each. Gas Valve and Humidifier will not be turned on.
G
R
Y
W
Com
HUM
TEST
STATUS
320615-102 REV. J
CONTINUOUS OFF - Check for 115VAC at L1 and L2, and 24VAC at SEC-1 and
SEC-2.
CONTINUOUS ON - Control has 24V power.
RAPID FLASHING - Line voltage (115V) polarity reversed. If twinned, refer to
twinning kit instructions.
LED CODE
EACH OF THE FOLLOWING STATUS CODES IS A TWO DIGIT NUMBER WITH THE FIRST
DIGIT DETERMINED BY THE NUMBER OF SHORTFLASHES AND THE SECOND DIGIT BY
THE NUMBER OF LONG FLASHES.
STATUS
24V
11 NO PREVIOUS CODE - Stored status codes are erased when power
(115V or 24V) to control is interrupted or 48 hours after each fault is cleared.
12 BLOWER ON AFTER POWER UP (115V or 24V) - Blower runs for 90 seconds,
if unit is powered up during a call for heat (R-W closed).
13 LIMIT OR FLAME ROLL-OUT SWITCH LOCKOUT - Control will auto reset after
three hours unless flame roll-out switch or fuse link is opened, refer to #33.
14 IGNITION LOCKOUT - Control will auto-reset after three hours. Refer to #34.
21 GAS HEATING LOCKOUT - Control will NOT auto reset.
Check for:- Mis-wired gas valve -Defective control (valve relay)
22 ABNORMAL FLAME-PROVING SIGNAL - Flame is proved while gas valve is
de-energized. Inducer will run until fault is cleared.
Check for: - Leaky gas valve -Stuck-open gas valve
23 PRESSURE SWITCH (ES) DID NOT OPEN Check for:
- Obstructed pressure tubing. - Defective pressure switch (stuck closed).
24 SECONDARY VOLTAGE FUSE IS OPEN
Check for:- Short circuit in secondary voltage (24V) wiring.
31 PRESSURE, DRAFT SAFEGUARD, AUXILIARY-LIMIT (when used),OR BLOCKED
VENT SHUTOFF (when used) SWITCH DID NOT CLOSE OR REOPENED - If open
longer than five minutes, inducer shuts off for 15 minutes before retry.
Check for: - Inadequate Combustion air supply.
- Proper vent sizing and condensate pitch or sag
- Low inducer voltage.
- Vent restriction or high winds.
- Disconnected or obstructed pressure tubing
- Defective inducer motor or start capacitor.
- Defective pressure switch or connections. If it opens after trial for ignition
period, blower will come on for 90 second recycle delay.
33 LIMIT OR FLAME ROLL-OUT SWITCH IS OPEN - If open longer than three
minutes, code changes to #13. Flame roll-out switchrequires manual reset.
Check for: - Defective blower motor or capacitor.
- Dirty filter or restricted duct system.
- Loose blower wheel.
- Defective switch or connections.
- Inadequate Combustion air supply (Flame Roll-out Switch or fuse link).
- Open Flame Roll-out switch,or fuse link. Manual reset or replace.
34 IGNITION PROVING FAILURE - Control will try three more times before a
lockout #14 occurs. If flame signal lost after trial for ignition period, blower
will come on for 90 second recycle delay. Check for:
- Oxide buildup on flame sensor (clean with fine steel wool).
- Proper flame sense microamps (.5 microamps D.C. min., 4.0 - 6.0 nominal).
- Gas valve defective or gas valve turned off.
- Defective Hot Surface Ignitor
- Manual valve shut-off.
- Low inlet gas pressure.
- Green wire MUST be connected to furnace sheet metal.
- Inadequate flame carryover or rough ignition.
If status coderecall is needed, do not remove power or blower door. Briefly remove and then
reconnect one main limit wire to display stored status code.
987
654
321
12

Is circuit breaker closed? Close door switch and go to start.Is red LED status light on? Is door switch closed?
Is red LED status light blinking rapidly without a pause?
Is there 115v going to switch? Replace door switch.Replace control center. Replace transformer.
Is red LED status light blinking ON/OFF slowly with a combination of short and long flashes?
Check for correct line voltage polarity. If units are twinned, check for proper low-voltage (24v) transformer phasing. Check for previous fault by momentarily shorting the TEST terminal and the C terminal until the LED goes out. LED will flash the status code of any previous fault or the code No. 11 (1 short and 1 long flash) if no previous fault. After the control repeats the code 3 times, the control will go through a brief component test sequence. The inducer will start and run for the entire component test. The HSI, blower motor heat speed, and blower motor cool speed will run for 10-15 sec each.
Determine status code. The status code is a 2 digit number with the first digit determined by the number of short flashes and the second digit by the number of long flashes.
Was there a previous fault code other than No. 11? Does control respond to W, Y,
or G 24-vac thermostat signals? Run system through a heating or cooling cycle to check operation. Status codes are erased after 48 hrs or whenever power (115v or 24v) is interrupted.
Go to section with status code determined.
Is there 115v at L1 and L2?
Close circuit breaker and go back to start.
Check for continuity in wire from circuit breaker to furnace.
NO NO NO
NO NO
NO
YES
YES YES
YES YES
YES
YES
NO
NO YES YES
YES
START
Is there 24v at SEC-1 and SEC-2?
NO Is 24 vac present at W, Y, or G
terminals on the control? Replace control if it does not respond to 24-vac signal at W, Y, or G screw terminals. Check room thermostat or interconnecting cable.
YES NO
NO
→Troubleshooting Guide
13

11 NO PREVIOUS FAULT - Faults
are erased after 48 hrs or whenever power (115v or 24v) is interrupted. Run system through a heating or cooling cycle to check system.
12 BLOWER ON AFTER POWER
UP (115V OR 24V) - Normal operation. Blower will run for 90 sec when furnace power is interrupted during a call for heat, R-W closed.
13 LIMIT OR FLAME ROLLOUT
SWITCH LOCKOUT - Limit switch was open longer than 3 minutes. Auto-reset will occur after 3 hrs. Flame rollout switch requires manual reset. See No. 33
14 IGNITION LOCKOUT - System
failed to ignite gas and prove flame in 4 attempts. Control will auto-reset in 3 hrs. See No. 34
21 GAS HEATING LOCKOUT -
Turn off power and wait 5 minutes to retry. Check for:
Unplug ignitor harness from control center and inititate another component test sequence. Check for 115v between pins 1 and 2 on the control center. Was 115v present for the 17-sec period?
Replace control center.
Check for continuity in the harness and ignitor. Replace defective component.
Reconnect the R thermostat lead and set thermostat to call for heat. Connect voltmeter across gas valve connections. Does gas valve receive 24v?
Check connections. If OK, replace control center.
Does gas valve open and allow gas to flow? Check that all gas valves are turned
on. Replace valve.
Do main burners ignite? Do main burners stay on? Allow blower to come on and repeat test to check for intermittent operation.
Repeat call for heat and check flame sensor current during trial for ignition period. Is the DC microamps below 0.5?
Check connections and retry. If current is near typical value and control will not stay on, replace control center.
Clean flame sensor with fine sandpaper and recheck current. Current is nominally 4.0 to 6.0 microamps. Is current near typical value? Replace electrode. Will main burner ignite and stay on? Replace control center. Fixed.
• Stuck closed gas valve relay
on control.
• Miswire or short to gas valve
wire.
22 ABNORMAL FLAME PROVING
SIGNAL - Flame was sensed while gas valve was de-energized. Inducer will run until fault is cleared. Check for: • Stuck open gas valve solenoid
or leak.
• Defective control center.
23 PRESSURE SWITCH WILL
NOT OPEN - Check for: • Disconnected or obstructed
pressure tubing.
• Defective pressure switch.
24 LOW-VOLTAGE FUSE IS
OPEN - Check for: • Short in low-voltage wiring
including thermostat leads shorting to ductwork or furnace cabinet. Disconnect thermostat leads to isolate short circuit.
31 PRESSURE SWITCH WILL
NOT CLOSE OR REOPEN - If open longer than 5 minutes, inducer shuts off for 15 minutes before retry. Check for:
• Proper vent sizing or pitch or
sag.
• Vent restrictions or high winds. • Defective inducer motor. • Low line voltage (115v). • Motor start capacitor. • Low inlet gas pressure. • Defective pressure switch or
connections. If it opens after trial for ignition period, blower will come on for 90 sec recycle delay.
• Inadequate combustion air.
33 LIMIT OR FLAME ROLLOUT
SWITCH IS OPEN - If limit switch is open longer than 3 minutes, code changes to No. 13. Check for: • Blower motor failure. • Motor start capacitor. • Open flame rollout switch,
manual reset.
• Dirty filter. • Defective limit switch or
connections.
• Loose blower wheel.
34 IGNITION PROVING FAILURE -
If flame is not sensed during the trial for ignition period, the control will repeat the ignition sequence 3 more times before going into lockout, No. 14. If flame signal is lost after trial for ignition period, blower will come on for 90-sec recycle delay. Check for the following items first before proceding to the next step. • Gas valve turned off. • Manual shut-off valve. • Green wire must be connected
to furnace sheet metal.
To determine whether the problem is in the gas valve, ignitor, or flame sensor, the system can be operated in the component test mode to check the ignitor. First, remove the R thermostat connection from the control center and initiate the component test sequence. Does the ignitor glow orange/white hot by the end of the 17-sec warm-up period?
Check for:
• Inadequate flame carryover on
rough ignition.
• Low inlet gas pressure.
NO
YES
YES YES YES YES YES
YES YES YES
NO NO
NO NO NO NO NO
•Inadequate combustion air
supply (flame rollout switch only).
NO
A99123
14

15

A94328
SERVICE TRAINING
Packaged Service Training programs are an excellent way to increase your
knowledge of the equipment discussed in this manual, including:
 • Unit Familiarization • Maintenance
 • Installation Overview • Operating Sequence
A large selection of product, theory, and skills programs is available, using popular
video-based formats and materials. All include video and/or slides, plus companion
book.
Classroom Service Training plus "hands-on" the products in our labs can mean
increased confidence that really pays dividends in faster troubleshooting, fewer
callbacks. Course descriptions and schedules are in our catalog.
CALL FOR FREE CATALOG 1-800-962-9212
[ ] Packaged Service Training [ ] Classroom Service Training
Copyright 1999 CARRIER Corp. • 7310 W. Morris St. • Indianapolis, IN 46231 58mxa6sm
Manufacturer reserves the right to discontinue, or change at any time, specifications or designs without notice and without incurring obligations.
Book 1 4
Tab 6a 8a PC 101 Catalog No. 535-745 Printed in U.S.A. Form 58MXA-6SM Pg 16 5-99 Replaces: 58MXA-5SM