HydroTherm MultiPulse AM Series User manual

AMP8-1203
AM SERIES PULSE BOILER
TROUBLESHOOTING GUIDE
FOR CERTIFIED CONTRACTORS ONLY
®
5211 CREEKBANK ROAD
MISSISSAUGA, ONTARIO L4W 1R3 CANADA
[phone] • FAX [phone]
260 NORTH ELM STREET
WESTFIELD, MA 01085
[phone] • FAX [phone]

2
TABLE OF CONTENTS
SECTION 1: OPERATION
Boiler Operating Lights - Location and function..................................................................................................3
Sequence of Operation (with lights) ...................................................................................................................3
Wiring Diagrams (AM-100/-150/-300)................................................................................................................ 5
Lighting and Operating Instructions................................................................................................................... 8
SECTION 2: TROUBLE SHOOTING
Preliminary Operational Check...........................................................................................................................9
- Boiler is not running:
Condition GC-4A Light Red Light Amber Light
A Off Off Off ....................................9
B Off Off On ..................................10
C Off On...................................................................11
D On ...................................................................................................12
E Blinking ...............................................................................................13
- Boiler is running:
Condition 1. Boiler ignites: runs for 8 seconds then shuts off .......................................................15
Condition 2. Boiler attempts ignition (8 seconds) - shuts off with a “cough” or no ignition............16
Condition 3. Boiler is “short cycling”..............................................................................................19
Condition 4. Boiler and condensate water leaks ...........................................................................22
Condition 5. Boiler noise (control and adjustment) .......................................................................24
a) Prolonged stutter on start-up .......................................................................................25
b) Combustion/operating noise ........................................................................................26
c) Vibration noise .............................................................................................................27
d) Objectionable exhaust noise........................................................................................27
e) Objectionable (localized)..............................................................................................28
SECTION 3: SERVICING/REPAIR PROCEDURES
Service Tools List .............................................................................................................................................29
Fan Pressure Check.........................................................................................................................................29
Gas Supply Pressure Check ............................................................................................................................29
Gas Input Rate Check (Metered and Differential Methods)..............................................................................30
Adjusting Input Rate .........................................................................................................................................30
Flue Box Adaptor Repair (AM-300) ..................................................................................................................30
Fan Inlet Gasket Replacement (AM-300) .........................................................................................................31
Air Inlet Orifice Repair (AM-300) ......................................................................................................................31
Igntion Wire Check ...........................................................................................................................................31
Wire Harness Assembly Replacement (AM-100 and 150) ...............................................................................31
Exhaust Cushion Chamber (ECC) and/or “O” Ring Replacement (AM-100 and 150)......................................33
Disassembling AM-300 Boiler ......................................................................................................................... 33
Leak Check (AM-300).......................................................................................................................................35
-Reassembly AM-300 Boiler ......................................................................................................................35
-Reposition Boiler in it's location (AM-300) ................................................................................................36
Heat Exchanger Replacement (AM-100 and 150)............................................................................................37
Boiler Reassembly (AM-100 and 150)..............................................................................................................37
Quick-Check Trouble Shooting Guide – GC-4A ...............................................................................................39
SECTION 4: REPLACEMENT PARTS LIST
Part Identification/Figs. 9 thru 12 (AM-100 / -150 / -300) .................................................................................40

3
SECTION 1: OPERATION
AMBER Part of 115V ON-OFF rocker switch
LIGHT (SW1). Side of electric box (AM-100 and
AM-150). Front top of boiler (AM-300). Lit
when switch is on.
RED Top of electric box (AM-100 and AM-150).
LIGHT Front top of boiler (AM-300). Lit when
all operational controls are calling for heat
and 24V is supplied to the GC-4A ignition
control.
GREEN Top of electric box (AM-100 and 150).
LIGHT Front top of boiler (AM-300). Lit when
gas valve is energized (24V).
BOILER OPERATING LIGHTS
GC-4A On GC-4A ignition control - visible thru a
LIGHT cutout in control cover near the 6-pin
Molex connector. OFF when no 24V to
control (no call for heat). Lit when boiler is
running,GC-4Aisinignitionsequenceoron
“hold” - refer to operating sequence.
“Blinking” when GC-4A is in “lockout” or in
the middle of a retrial period.
LAMP Red and green bulbs can be checked with
CHECK Volt/ohm meter: disconnect the lamp from
the circuit and check across the leads for
continuity. Replace any burned out lights
or loose wiring.
SEQUENCE OF OPERATION (WITH LIGHTS)
1. GasOn/PowerOn. WithRockerswitchSW1(On/Off
switch) closed (amber light is ON) 115/24V
transformer is powered. Refer to figure 1, 2 or 3
for boiler wiring diagrams.
2. Boilerthermostatcallsforheat;“T-T”contactsCLOSE;
and circulator relay R1 (AM-100 and AM-150 only)
is energized. The circulator relay contacts
(C1R1) close starting the circulator pump
(AM-100/-150).
3. 24 volts is also supplied to the high limit. If the
limit (automatic reset type) is “OPEN” (Red Light
OFF) due to high water temperature, the ignition
controlwaits until limitcloses. When thelimit closes
(Red Light ON), the GC-4A ignition control is
energized (GC-4A Light ON) and checks the
position of the Combustion Prove Switch (PS1)
contacts (N.O.- NORMALLY OPEN). On AM-150,
the blocked inlet switch (PS3) contacts
(N.C.-NORMALLY CLOSED) are also checked. If
the(PS1) contacts areOPEN and the(PS3)contacts
(AM-150 only) are “CLOSED”, the GC-4A control
will begin the timed ignition sequence. If either or
bothof the pressure switchcontactsis inanincorrect
position, the GC-4A goes on “HOLD” (Red Light
“ON”; GC-4A Light “ON”) unti switch position is
corrected.
4. With the above condition satisfied, the GC-4A
control will begin a timed pre-purge sequence
(35-seconds); start the fan; and check the fan
Prove Switch (PS2) contact position. This switch
contact (N.O.), must close proving blower operation
before any gas ignition will occur. If the Fan Prove
Switch (PS2) contacts are “CLOSED” after the
initial 35-second pre-purge, the control will continue
with an attempt for gas ignition. If the (PS2)
contacts remain “OPEN” there will be no attempt
for ignition (no spark or gas valve will energize)
but, the fan will continue to run. After an additional
26-seconds, the control will recheck the contacts
on (PS2). If the contacts remain open, again
there will be no attempt for ignition and the fan will
continue to run. The control will check the contact
on switch (PS2) three more times at 26-second
intervals. If the contacts remain open, there will
be no attempt at ignition. After the fifth check of
the contacts, the fan will remain energized for a
30-secondpost-purgeperiod,afterwhichtheignition
sequence will end and the GC-4A light will begin to
blink (Red Light ON) indicating “LOCKOUT”
(temporary). This ignition sequence will have
taken 2 min. 45 seconds. Fifteen minutes later, the
control will automatically begin a second ignition
sequence attempt. If the condition remains
uncorrected the retry sequence above will be
repeated up to 10 times before a 100% system-
lockout occurs. See “AUTOMATIC RESTART
FEATURE” section.

4
5. The ignition sequence (8 sec. duration) is controlled
by the module which provides a spark at the spark
plug & energizes the gas valve (Green Light “ON).
The pre-purge blower continues to operate during
this period.
If ignition occurs during the 8-second attempt, the
combustionpressureis sensed by the Prove Switch
(PS1)withswitch contact (R-W) closing andproving
combustiontotheGC-4Acontrol.Thefanandignitor
are then shut off; the gas valve remains energized;
boiler runs (Red Light ON; Green Light ON) and the
GC-4A control timer circuits are reset. Fan Prove
Switch (PS2) senses the fan shutdown and (PS2)
contacts open. Boiler operation will continue until
“Call for Heat” is satisfied.
If ignition does not occur during the 8-second trial
period, the spark and gas valve will be
“de-energized” (Red Light ON; Green Light OFF)
and the fan will continue to run. After 26-seconds, if
the (PS2) contacts are closed, the control will
initiateasecond8-secondtrialforignition(RedLight
ON;GreenLight ON). This sequence of26-seconds
OFF, 8-seconds ON, will occur 3 more times. If,
after the fifth trial for ignition, combustion is not
sustained, the ignitor and gas valve will be
de-energized and the fan will continue for a
30-second post-purge, after which it will shut off.
This ignition sequence will have taken 3 min.
30sec.(RedLightON;GreenLightOFF;GC-4Alight
blinking). The GC-4 control is on “Temporary
Lockout”. Fifteen minutes after completing this
ignition sequence, the control will automatically
initiate a second (5-trial) ignition sequence. See
“Automatic Restart Feature” section for additional
sequencing details.
AUTOMATIC RESTART FEATURE: The GC-4A ignition
control is equipped with an automatic reset feature. If
the control completes an ignition sequence (5 attempts
for ignition) without sustaining or proving gas ignition,
the control will go into a 15-minute “Temporary
Lockout” mode (GC-4A light blinking) after which the
control will initiate a second (5-trial) ignition sequence
(GC-4A Light ON). If combustion is not sustained during
the second ignition sequence, the control will again go
on a 15-minute “Temporary Lockout”, followed by
another ignition sequence. This pattern will repeat an
additional 10 times (3 hours 45 minutes total), at which
time the control will produce a 100% “System Lockout”
(GC-4A light blinking), requiring an operating
control or line switch reset. To reset the boiler during
any of the ignition sequences or from the “100%
Lockout” condition, momentarily de-energize the
ignition control by switching the rocker switch OFF and
ON. This resets the module to the initial starting mode
of the first ignition sequence.
HI-LIMIT OPERATION: If, during the run mode, the
water temperature exceeds the limit setting, its
contacts will open and the boiler will shut down (Red
Light OFF; Green Light OFF; GC-4A Light OFF).
However, relay R1 operating the circulating motor
(AM-100 and AM-150) will remain energized. After the
water temperature drops below the limit set point it’s
contacts close (Red Light ON) and the ignition sequence
is repeated (GC-4A Light ON). Refer to step #3.
“CALL FOR HEAT” SATISFIED: When the control
thermostat is satisfied, its contacts will open,
de-energize gas valve; relay R1 (AM-100/-150) and
shut the boiler off. (Red Light OFF; Green Light OFF,
GC-4A Light OFF). The ignition module resets await-
ing the next call for heat.

5
FIGURE 1
AM-100 SCHEMATIC & LADDER WIRING

6
FIGURE 2
AM-150 SCHEMATIC & LADDER WIRING DIAGRAM

7
FIGURE 3
AM-300 SCHEMATIC & LADDER WIRING DIAGRAM

8
LIGHTING AND OPERATING INSTRUCTIONS
(Honeywell VR-8305M Gas Valve)
WARNING:
If you do not follow these instructions exactly, a fire or explosion may result causing properly
damage, personal injury or loss of life.
C. Use only your hand to turn gas control knob. Never
usetools.Iftheknobwillnotturnbyhand,don'ttryto
repair it; call a qualified service technician. Force or
attempted repair may result in a fire or explosion.
D. Do not use this appliance if any part has been under
water. Immediately call a qualified technician to
inspect the appliance and to replace any part of
the control system and any gas control which has
been under water.
TO TURN OFF GAS TO BOILER
1. Set thermostat to lowest setting.
2. Turn off all electrical power to the appliance if
service is to be performed.
3. Turn gas control knob clockwise to “OFF”.
Do not force.
LIGHTING INSTRUCTIONS
1. STOP! Read the safety information above on this
page.
2. Set the thermostat to lowest setting.
3. Turn off all electrical power to the boiler.
4. This appliance is equipped with an ignition device
which automatically lights the burner. Do not try to
light the burner by hand.
5. Turn gas control knob clockwise to “OFF”.
Do not force!
6. Wait(5)fiveminutestoclearoutanygas.Thensmell
for gas, including near floor. If you smell gas STOP!
Follow “B” in the safety information above on this
page. If you don't smell gas, go to the next step.
7. Turn gas control knob counterclockwise
to “ON”.
8. Turn on all electrical power to boiler.
9. Set thermostat to desired setting.
10. If the appliance will not operate, follow the
instructions “TO TURN OFF GAS TO BOILER” and
call your service technician or gas supplier.
OFF
ON
GAS INLET GAS OUTLET
GAS CONTROL KNOB SHOWN
IN "ON" POSITION
LIGHTING INSTRUCTIONS AM-100/150/300
A. This appliance does not have a pilot. It is equipped
withanignition device which automatically lights the
burner. Do not try to light the burner by hand.
B. BEFORE OPERATING smell all around the
appliance area for gas. Be sure to smell next to the
floor because some gas is heavier than air and will
settle on the floor.
WHAT TO DO IF YOU SMELL GAS
• Do not light any appliance.
• Do not touch any electric switch; do not use any
phone in your building.
• Immediatelycallyourgassupplierfromaneighbor's
phone. Follow the gas supplier's instructions.
• If you cannot reach your gas supplier, call the fire
department

9
SECTION 2: TROUBLE SHOOTING
2. If the boiler is running, but exhibits one of the
following conditions, observe the operating
light conditions and use the procedure(s) under
the appropriate heading on the referenced page(s)
noted.
IF BOILER IS OPERATING (CONDITIONALLY):
REF.
CONDITION DESCRIPTION PAGE
1 Boiler ignites (8 sec.)
but shuts-off 15
2 Boiler cycles but
won’t light 16-19
3 Boiler “short-cycling” 19-21
4 Boiler condensate
water leaks 22-23
5 Boiler noise -
control/adjustment 24-28
CONDITION A
GC-4 LIGHT OFF; RED LIGHT OFF; AMBER LIGHT OFF.
This indicates no 115V to the boiler.
POSSIBLE CAUSE VERIFICATION SOLUTION
Power Supply With a voltmeter, check for 115V. If no 115V, check circuit breaker at
On AM-100 & 150 terminals1 & 4. disconnect switch and supply wiring.
On AM-300 terminals 1 & 3. Connect if necessary.
If 115V, proceed with this check.
Rocker Switch With a voltmeter, check for 115V. If no 115V, operate switch. If no
On AM-100 & 150 terminals 3 & 4. 115V, check wiring to switch.
On AM-300 terminals 2 & 3. If ok replace switch.
If 115V but no amber light, proceed
with check.
Amber Light With a voltmeter, check for 115V If 115V, replace switch.
across terminals 2 & 3 on Rocker
Switch. If no 115V, check wiring.
CAUTION: Label all wires prior to disconnection
when servicing controls. Wiring errors can cause
improper and dangerous operation.
Verify proper operation after servicing.
PRELIMINARY OPERATIONAL CHECK
RefertoSection3-“SERVICINGPROCEDURES”forlist
of service tools.
1. UPON ARRIVAL AT SERVICE CALL: First - check
the status of the boiler operating lights. If the
boiler is not running, follow the procedures under
the appropriate heading on the referenced pages
below.
IF BOILER IS NOT RUNNING:
GC-4A RED AMBER REF.
CONDITION LIGHT LIGHT LIGHT PAGE
A OFF OFF OFF 9
B OFF OFF ON 10
C OFF ON * 11
DON**12
E Blinking * * 13-14
*Lights OFF indicate burned out bulb or loose wiring.

10
CONDITION B
GC-4A LIGHT OFF, RED LIGHT OFF, AMBER LIGHT ON
Turn Rocker Switch OFF and ON. If, within 10 seconds, the GC-4A light comes ON proceed to “CONDITION “E”.
Replace Red Light (if OFF). If GC- 4A light remains OFF, proceed with check.
POSSIBLE CAUSE VERIFICATION SOLUTION
Operational Control(s) Turn Rocker Switch OFF. Place a If GC-4A and/or Red Lights come ON
jumper across T-T terminals. check thermostat and other
Turn Rocker Switch ON. operational controls and adjust or
replace as necessary.
If lights remain OFF, proceed with
check.
High Limit (Keep T-T jumper in place). Turn If GC-4A and/or Red Lights come ON,
Rocker Switch OFF. Jumper the high limit is set too low or defective.
high limit terminals. Turn Rocker Compare supply water temperature
Switch ON. and limit setting. If settings are
proper, replace limit.
If lights remain OFF, high limit is OK.
Transformer Rocker Switch ON. With a voltmeter, If no 24V, replace transformer.
check for 24V across T-T terminals
to ground. If 24V transformer is OK, proceed
with check.
AT THIS POINT RED LIGHT SHOULD BE ON - IF NOT, REPLACE LAMP
GC-4A Ignition Control Turn Rocker Switch OFF. Disconnect If 24V, reattach connector to GC-4A.
6-pin Molex connector from GC-4A. If GC-4A light remains OFF, replace
Turn Rocker switch ON. With a GC-4A (and Red lamp if OFF).
voltmeter, check for 24V from pin 2
(brown wire) on connector to ground. If no 24V, check wires (incl. grounds)
REMOVE ANY JUMPERS USED and wire connections until 24V
FOR TEST. is established. If necessary, replace
wire harness.
NOTE: Non-resistive spark plugs (i.e. - Champion WR-18, etc.) must never be used in combination with a GC-4
ignition module. Use only approved, resistance spark plugs (Champion FI-21503). High-voltage ignition
wiring must never contact remaining boiler wiring.

11
CONDITION C
GC-4A LIGHT OFF, RED LIGHT ON
Turn Rocker Switch OFF and ON. If, within 10 seconds, the GC-4A light come ON, proceed to CONDITION “E”.
If after the toggle switch is turned “OFF” and “ON”:
- GC-4A light remains “OFF”.
- Red light is “ON” but there is no “Prepurge Cycle” or blower operation initiated (unit is in standby mode).
- Green light “ON” immediately - but no gas flows to unit. The ignition module has lost ground continuity
between the module and ground. Replace terminal connection on the end of ground wire (green)
leaving the module.
If GC-4A light remains OFF, proceed with this check.
POSSIBLE CAUSE VERIFICATION SOLUTION
Wiring Check if green ground wire from If screw is loose, secure screw. If
GC-4A is securely fastened to the wires are not on a common screw
ground screw. Also check rewire the grounds.
transformer ground. If GC-4A light remains OFF, proceed
with check.
GC-4A Ignition Control Turn Rocker Switch OFF. If 24V, reattach connector to GC-4A.
Remove 6-pin Molex connector from If GC-4A light remains OFF after 10
GC-4A. Turn Rocker Switch ON. seconds replace GC-4A.
With a voltmeter, check for 24V from
pin 2 (brown wire) on connector to If no 24V, check wiring and
ground. connectors until 24V is established.

12
CONDITION D
GC-4A LIGHT ON
(If Red or Amber lights are OFF, replace lamp or switch.) Boiler may be in an ignition seqence - wait 40 seconds
for an attempt at ignition (Green Light ON).
If there is no attempt at ignition: turn Rocker Switch on boiler OFF and ON. Observe and clock the time the GC-4A
light is ON.
- If within 45 seconds, the Green Light is lit; or there is an audible attempt at ignition, proceed to condition “E”.
- If the GC-4A light is blinking after 3 min. 45 sec., proceed to condition “E”.
- If the GC-4A light is ON after 3 min. 45 sec. with no attempt at ignition, proceed with check below.
POSSIBLE CAUSE VERIFICATION SOLUTION
Combustion Prove Pressure Turn Rocker Switch OFF. Remove If boiler has attempted ignition
Switch PS1 (N.O. Contacts) one purple wire from PS1 Pressure (Green Light ON) and the GC-4A light
- Pressure Switch adjusting Switch. Turn Rocker Switch ON, is blinking. Pressure Switch is
is factory set at 5" W.C. wait 3 min. 45 sec. defective. Replace switch.
If GC-4A remains ON, Pressure
Switch is ok. Reconnect purple wire
and proceed with check.
Blocked Inlet Pressure Turn Rocker Switch OFF. Jumper If boiler is running, replace Pressure
Switch (PS3) (N.C. Contacts) Pressure Switch PS3 Terminals. Switch.
(Factory setting fixed) Turn Rocker Switch ON. Wait
Supplied on AM-150 only 3 min. 45 sec. If GC-4A light is blinking, replace
Pressure Switch (PS3) and proceed
to condition “E”.
If GC-4A light is ON, Pressure Switch
is ok. Proceed with check.
Wiring Turn Rocker Switch OFF. Remove If no continuity, check wiring until
the 6-pin Molex connector from the continuity is obtained.
GC-4A control. With and ohmmeter
check for continuity from pin 5 If continuity, reattach connector to
(Lt Blue wire) to pin 1 (White wire) GC-4A. Turn Rocker Switch ON.
on the supply wiring side of the If after 3 min. 45 sec. the GC-4A
connector plug. light is on (not blinking) replace GC-4A .
NOTE: On the AM-150 contacts
on PS-3 should be closed.

13
CONDITION E
GC-4 LIGHT BLINKING
Turn the Rocker Switch OFF and ON. Observe GC-4 light and clock ON time before it begins to blink.
If Red or Amber Lights OFF, replace lamp or switch.
If the boiler starts and runs, a temporary problem may have corrected itself, (I.E., low gas pressure or a blockage
of the inlet, etc). However, there may also be a slow draining condensate or a partially blocked exhaust, see
Blocked Exhaust under “CONDITION #2B”. Stop and start the boiler a number of times to assure normal
operation has been restored.
If boiler does not ignite or ignition is rough - see “CONDITION 2.”
If GC-4A light is ON 3 min, 30 sec., then starts blinking and boiler attempted ignition - proceed to “CONDITION 2”.
If GC-4A light is ON 3 min, 30 sec., then starts blinking and if boiler “coughs” or does not attempt ignition, pro-
ceed to “CONDITION 2”.
If GC-4A light is ON 2 min, 45 sec., then begins to blink, measure fan pressure (see “PROCEDURES” section)
and use one of the two procedures below.
MODEL NO. MINIMUM FAN PRESSURE (PS2)
AM-100/-150 +1.4" W.C.
AM-300 +0.8" W.C.
1. If measured fan pressure exceeds the minimum for fan prove switch (PS2) operation.
POSSIBLE CAUSE VERIFICATION SOLUTION
Wiring Turn Rocker Switch OFF. Remove If no continuity, check wire and
the 6-pin Molex connector from the connectors until continuity is
the GC-4A. (Keep Fan Switch (PS2) obtained - reconnect Molex to GC-4A
jumper in place). With an Ohm- and run Fan Prove Switch check.
meter check for continuity across
pin-4 (grey) and 5 (lt.blue). If continuity but, condition above
exists-replace GC-4A.
Fan Prove Switch (PS2) **Turn Rocker Switch OFF. Turn If boiler starts, (PS2) pressure
(N.O.) contacts Rocker Switch ON. Jumper pressure switch is defective - replace it.
(Factory Fixed Setting) switch (PS2) contacts. If the GC-4A light begins to blink after
2 min. 45 sec., (PS2) switch is ok.
Proceed with check.
If the boiler attempts to start and the
GC-4A light blinks after 3 min.30 sec.,
(PS2) switch is defective - replace it.
** NOTE: Fan must be operating before placing jumper across swith PS2. Always remove jumper before resetting
boiler.

14
CONDITION “E” continued…
2. If measured fan pressure is at or below the minimum for Fan Prove Switch (PS2) operation.
POSSIBLE CAUSE VERIFICATION SOLUTION
Fan Motor Turn Rocker Switch and Gas Valve If you read 115V, proceed with
top knob OFF. Remove air cushion verification.
cover. (On AM-100 & -150 lift fan
assembly out of boiler and check If no voltage, check for open circuit
motor is securely fastened to the (see below).
mounting plate). Disconnect the fan
motor wire leads from the boiler
wiring at quick connects provided.
Turn the Rocker Switch ON. With a
voltmeter, check for 115V across the
supply leads from the boiler.
Turn Rocker Switch OFF. Reconnect If the motor runs, proceed with check.
fan leads to motor. (For AM-100 &
-150, place fan assembly on ledge If motor does not run, replace motor
of air cushion chamber). Turn fan assembly.
Rocker Switch ON.
AM-300 Blower Wheel - Turn Rocker Switch OFF. Remove If loose, secure blower wheel
Obstructed or loose fan from mounting studs and check properly on shaft. If obstructed
blower wheel is secure on shaft, not remove obstructions.
rubbing against housing and free
from obstruction. If ok, proceed with verification.
AM-300 Blocked Air Inlet Check for obstructions in air supply If obstructed, remove obstruction.
Orifice vent terminal and piping. On AM-300
check inlet orifice located in inlet If unrestricted, proceed with
adapter: see FIG. 7. verification.
AM-100 and 150 Check that impeller is firmly secured If broken replace impeller and/or
Broken Impeller to motor shaft. assembly.
Air Inlet Vent and Lines Check air inlet terminal for blockage If obstructed - clear vent inlet.
from freezing or debris. If clear, proceed with vent line check.
Check vent lines for sagging low
spots which can act as water If sagging is observed, support
trap and reduce the air supply. pipe to remove “traps.”
Open Fan Circuit Remove the three conductor Molex If no continuity, replace GC-4
GC-4A Control Checkout connector (with red and black wires) ignition control following instructions
from GC-4 ignition control. packaged with replacement.
CAUTION: 115 VAC supply. Turn If continuity is ok - check wiring.
Rocker Switch OFF and then ON.
Within 30 sec. check for continuity
across the two outer Molex connector
sockets on the ignition control
(Term. 1 & 3).

15
CONDITION “E” continued …
POSSIBLE CAUSE VERIFICATION SOLUTION
Wiring to GC-4A (115V) Turn Rocker Switch OFF. With an If no continuity on any wire, replace
ohmmeter, check continuity of red & or repair as required.
black wires of the 3-conductor Molex
connector. If all continuity checks ok, check if
motor wire terminals mate correctly
when joined.
Turn gas valve top knob to “ON” after
completing checkout.
CONDITION #1 - BOILER IGNITES (8 SECONDS) THEN SHUTS OFF
GC-4A Light is “ON”, Red Light “ON”, Green Light “ON” (during 8 second ignition trial). After 3 min. 45 sec (5
unsuccessful igntion trials) the GC- 4A light then blinks.
IF THE BOILER, WHEN IT RUNS, STOPS BEFORE THE GREEN LIGHT GOES OUT - PROCEED TO
“CONDITION #3.”
POSSIBLE CAUSE VERIFICATION SOLUTION
Copper Pressure Sensing Turn Rocker Switch OFF & remove Repair or replace as necessary.
Tube top from Air Cushion Chamber
(A.C.C.). (On AM-100 & -150 remove
Runs from Gas Cushion fan assembly). Check tube for breaks
Chamber (G.C.C.) valve at the GCC valve plate & on the
plate to Combustion AM-300 at the fitting on the ACC
Prove-Pressure Switch (PS1). wall. Check unions are tightly
connected.
Pressure Switch (PS1) If removed, replace fan assembly If boiler runs more than 9 seconds
(Combustion Prove Switch) and air cushion chamber top and (with jumper in place), replace switch
turn Rocker Switch ON. (PS1).
Immediately after boiler starts, place If boiler runs 8 seconds (stops when
jumper across PS1 pressure Green Light goes OFF) with the
switch terminals (R-W). DO NOT jumper in place, proceed with
PUT JUMPER ON UNTIL GAS verification.
VALVE IS ENERGIZED.
CAUTION: TERMINAL VOLTAGE
EXCEEDS 300 VOLTS.
(Remove jumper after test).
Wiring - Purple Wires (2) Check both purple wires from (PS1) If loose, reconnect wires. Repeat
From PS1 to GC-4A Ignition pressure switch to ignition control. Pressure Switch verification. If boiler
Control Connections must be secure to runs less than 9 seconds (with
complete circuit from module. jumper in place), switch is ok.
If no loose wires, replace GC-4A
ignition module following instructions
packaged with replacement.

16
CONDITION #2 - BOILER ATTEMPTS IGNITION (8 SECONDS) WITH ONLY A “COUGH” OR NO IGNITION:
THEN SHUTS OFF
GC-4A Light is “ON”; Red Light “ON”; Green Light “ON”; - during each 8 sec. ignition trial (5 attempts). Unit does
not run after 3 min. 45 sec. The GC-4 light then blinks.
NOTE: ON A START-UP, BOILER MAY LOCK OUT SEVERAL TIMES BEFORE ALL AIR IS PURGED FROM
GAS LINE.
MEASURE FAN PRESSURE (SEE “PROCEDURES” SECTION) AND USE ONE OF THE THREE PROCE-
DURES BELOW.
A. IF FAN PRESSURE MEASURES NORMAL: +1.5 to 1.9"W.C. for AM-100 & -150.
+1.0 to 1.4"W.C. for AM-300.
POSSIBLE CAUSE VERIFICATION SOLUTION
Gas Line Valves Check that all valves in gas line, Open all gas valves in gas line.
including combination gas valve,
are in open position.
Incorrect Gas Supply With manometer, check gas supply Adjust gas supply pressure as
Pressure (should be pressure as described in necessary.
between 4.5" to 7.0" W.C. “Procedures” section of this manual.
for Natural Gas;11” W.C.
for Propane Gas)
Combination Gas Valve Turn the Rocker Switch OFF and If no 24V & no green light, check
(24V) ON. After 35 seconds,with a wiring. If intact and secure - replace
voltmeter, check for 24V across the GC-4A.
gas valve terminals (MV-MV). If read 24V & green light OFF replace
green lamp and proceed with check.
Put manometer downstream of gas If no indication of gas flow, replace
valve. When gas valve opens gas valve.
(Green Light “ON”) gas pressure
should increase. (Manometer will If gas flow is confirmed, proceed
read a purge fan pressure before with check.
valve opens).
Check Ignition Circuit Turn Rocker Switch & Gas Valve If spark is strong, control is ok.
(GC-4 Ignition Control) top knob “OFF.” Turn Rocker Switch Reconnect ignition lead.
“On” & allow unit to purge to a
sequenced lockout (temporary). If no spark, check that the white
Turn Rocker Switch “OFF” and (neutral) lead is securely connected
remove high tension ignition lead from the “NEU” spade connection on
from ignition control. Turn Rocker ignition module to neutral side of the
Switch “ON” & after 34 sec. (purge), 24V transformer.
check for spark with insulated
screwdriver between the ignition If secure and not sparking, replace
control spud & ground. the GC-4 ignition control.
CAUTION: Hi-voltage Potential.

17
CONDITION #2 continued …
POSSIBLE CAUSE VERIFICATION SOLUTION
Ignition Lead Turn Rocker Switch “OFF.” Remove If no continuity or damaged lead -
cover from ACC. Remove the fan then replace wire harness assembly.
assembly on the AM-100 & -150. (See “Procedures” section).
With an ohmmeter, check lead for Reseal “ACC” chamber opening.
continuity. Visually check lead wire
and boot for tears, abrasions or If continuity & lead checks
“burn spots” indicating a short circuit. satisfactorily - proceed with
verification.
NOTE: Hi-voltage ignition lead
wiring must not contact regular If visual check is ok perform ignition
wiring on boiler. wire check (“Procedures”
section).
If ok proceed with verificaiton.
Spark Plug Turn Rocker Switch & Gas Valve If plug is ok - check gap (.100" to
Top Knob “OFF”. Remove spark .125") and reassemble in boiler.
Use only resistive-type plug from combustion chamber and
spark plug (Champion visually check for ceramic cracks, If plug is worn or ceramic cracked -
FI-21503): Replace any carbon tracks, and wear. Attach the replace plug.
non-resistive type plugs ignition lead to spark plug & place
(WR-18/etc.) plug on head of boiler. Jumper Fan If plug shows carbon tracks or
Prove Switch (PS2). Turn Rocker excessive carbon deposits, clean
Switch “ON” and observe the spark plug and proceed with check.
during the ignition sequence.
Input Rate Reassemble boiler.Turn Rocker If boiler won’t run & you suspect
Switch “OFF” & Gas Valve Top Knob “overfire”; check if pressure
“ON.”Turn Rocker switch “ON” regulator adjusting screw is
(start boiler). bottomed out. Turn screw
counterclockwise (in 1/4 turn
After boiler runs for at least 10 min. - intervals) to decease flow rate.
check input rate according to one After each adjustment replace
of two methods described under pressure regulator cap before
“Procedures” section of this turning “ON” boiler.
manual. Adjust gas valve regulator
as necessary to deliver desired If boiler won’t run & you suspect
input rate. “underfire”, check if adjusting screw
is topped out. Turn screw clockwise
To adjust pressure - turn OFF in 1/4 turn intervals to increase
boiler/remove regulator cap on flow rate. After each adjustment
gas valve. Replace regulator cap replace pressure regulator cap
(secure) before re-starting unit and before turning “ON” boiler.
determining effects of adjustment. “O-Ring” seal on regulator cap must
fit securely against valve when
operating boiler. Replace old/worn
O-Ring if necessary.

18
CONDITION #2 continued.....
B. IF FAN PRESSURE MEASURES “ABOVE - NORMAL” CONDITIONS:
+2.4" W.C. OR HIGHER ON AM-100 & -150
+1.6" W.C. OR HIGHER ON AM-300
POSSIBLE CAUSE VERIFICATION SOLUTION
Blocked Condensate Drain Remove condensate drain tube at If condensate begins to flow
rear base of boiler. Remove the continuously wait for flow to stop -
fitting & insert a wire into tapping to clean tapping and/or fitting
clear debris from drain hole. Wire thoroughly. Reassemble drain
must be inserted a minimum 3" thru system & check fan pressure. If fan
fitting to clear inside wall. pressure reading is “normal” range,
proceed to attempt to start boiler.
If no unusual condensate flow -
proceed with check.
Blocked Exhaust Line Check for a blockage in the exhaust If the measured pressure remains
line. Turn the boiler OFF. Attach a above “normal” and there is a muffler
manometer to the condensate drain in the exhaust line, proceed to
fitting of the boiler. Turn the Gas “BLOCKED MUFFLER” check. If no
Valve Top Knob OFF and the boiler muffler, examine exhaust line and
Rocker Switch ON. Observe the fan terminal for blockage.
pressure at the condensate drain
(ECC chamber pressure). On the AM-150 only
If the pressure is 0.2" W.C. or less,
recheck the fan pressure at electrical
box tee. If the fan pressure remains
high proceed with check.
Blocked Muffler Cut exhaust line after the muffler, If the pressure is still
allow at least 2" of pipe on each side “ABOVE-NORMAL” the muffler
of the cut for reassembly. Restart is blocked - cut it out-confirm
boiler and measure the fan pressure blockage and replace it.
at the condensate drain fitting. If the pressure is 0.2" W.C., or less,
the muffler is ok. Check the exhaust
line & vent terminal for a blockage.
Exhaust Cushion Cut exhaust line as close to boiler as If fan pressure returns to normal ECC
Chamber (ECC) possible (2" from fitting). Check fan is ok.
AM-150 Only pressure at condensate drain fitting. If pressure remains
NOTE: Rejoin/reseal any exhaust “ABOVE-NORMAL” & no water is
piping cuts made by check found in vent line, back flush the
procedures. Return Top Knob of Gas ECC to remove any blockage from
Valve to “ON” position. the ECC muffler tube. Remove ECC
and clear obstruction if back flush
does not correct blockage.

19
CONDITION #2 continued.........
C. IF FAN PRESSURE MEASURES “BELOW-NORMAL” CONDITIONS:
• LESS THAN 1.45" W.C. ON AM-100 & -150
• LESS THAN 1.0" W.C. ON AM-300
POSSIBLE CAUSE VERIFICATION SOLUTION
Air Inlet Pipes/Fan Assembly Turn “OFF” Rocker Switch. Turn gas If fan pressure increases to normal
(AM-100 & -150 Only) valve top knob OFF. Remove lid range, check the inlet piping, inlet
from ACC. Turn Rocker Switch “ON” muffler & inlet vent terminal for
and hold fan assembly firmly in place obstruction.
in its typical mounting position.
Observe fan pressure (see If fan pressure remains the same,
“Procedures” section - repair or replace fan assembly. If
“FAN PRESSURE.”) ok - proceed with check.
Obstructed Turn Rocker Switch and Gas Valve If loose, secure blower wheel
or Loose Blower Wheel top knob OFF. Remove Air Cushion properly on shaft. Remove
(AM-300) Chamber cover. Remove fan from obstructions. If ok proceed with
mounting studs & check blower check.
wheel is secure on shaft,not rubbing
against housing & free from
obstruction.
Fan Assembly Hold fan assembly in typical If motor runs ok - check for inlet vent
(AM-300) mounting position & turn Rocker restriction including inlet air orifice
Switch ON (gas OFF). Observe fan located in inlet adapter on AM-300.
operation and direction of rotation. See FIG.7.
(DO NOT LUBRICATE MOTOR). If motor runs slowly, replace
assembly.
Fan Inlet Gasket Check for compression marks on If gasket is not sealed properly,
(AM-100 & -150 only) gasket for complete seal to air inlet replace it. See “Procedure”
adapter & that gasket seals section in this manual for details.
completely (360-degrees) around
fan inlet opening.
CONDITION 3 - BOILER IS SHORT-CYCLING
Boiler ignition occurs, strong start but runs only short time (red and green lights on) and then suddenly stops. If
lights are operational, observe lights as detailed below and follow appropriate procedures.
• IF BOTH RED & GREEN LIGHTS GO OUT WHEN BOILER STOPS, BOILER IS RESPONDING TO AN
OPERATIONAL CONTROL THAT IS SATISFIED. CHECK SET POINTS ON HI-LIMIT, CIRCULATOR,
THERMOSTAT AND OTHER BOILER CONTROLS. ADJUST AS NECESSARY.
• IF GREEN LIGHT GOES OFF WITHIN SECONDS AFTER BOILER STOPS; RED LIGHT STAYS ON;
AND BOILER DOES NOT RESTART. PROCEED WITH (3B) CHECK BELOW.
• IF GREEN LIGHT GOES OFF WITHIN SECONDS AFTER BOILER STOPS; RED LIGHT STAYS ON;
BUT BOILER IMMEDIATELY RESTARTS, PROBLEM IS COMBUSTION RELATED. PROCEED WITH
OPERATIONAL CHECK BELOW (3A).

20
CONDITION 3A - BOILER SHORT CYCLES BUT AUTOMATICALLY RESTARTS
POSSIBLE CAUSE VERIFICATION SOLUTION
Recirculation of Exhaust Visually check air inlet terminal(s) for If there is recirculation, temporarily
at Inlet Terminals exhaust recirculation (vapor path). extend exhaust vent. If this
eliminates problem, proceed with
NOTE: On thru-the-wall installations permanent fix.
the exhaust should extend a
minimum 12" beyond the inlet If no recirculation proceed with
terminal. trouble shooting procedures.
Recirculation of Exhaust - Turn Rocker Switch & Gas Valve top (1) If valve discs have torn edges or
Internal knob to OFF. Remove lid from Air holes - replace discs.
Cushion Chamber (ACC). On (2) If foreign particles are between
AM-100 & -150 remove the fan valve plate & valve retaining
assembly. Remove the gas plate, remove them.
Cushion Chamber (GCC) & check (3) If valve discs are missing, replace
the bottom of the valve plate. GCC them.
valve discs must move freely and not (4) If valve discs are “wrinkled” and
bind. stiff - replace them and check
condensate drain and exhaust
line for partial blockage.
Check GCC gasket for crimps or If crimps, carbon trails, replace
carbon trails. gasket following instructions with
replacement.
If ok, proceed with verification.
Recirculation of Exhaust - With GCC removed, remove If O-ring has burned, hardened or
Internal combustion chamber inlet (flame has decomposed sections, check
(AM-300 Only) trap assembly). Check if O-ring adjoining chamber and chamber
between Combustion Chamber & inlet surfaces for obstructions which
inlet is intact. Check mating surfaces may prevent flush mating of the two
of inlet and combustion chamber. surfaces. Remove any obstructions,
These must be clean and free of clean O-ring groove and replace
debris before re-assembly. O-ring. (See “Procedures” section).
If O-ring is ok proceed with trouble-
shooting procedures.
Flame Trap (LP Boilers) With GCC removed, check that If any problems are evident, correct
(AM-100 & -150 Only) flame trap seats properly (no or replace the flame trap. If in doubt,
movement or rocking). Corrugated replace flame trap and run boiler to
strips should be flush with flange see if problem is corrected.
face (not coned) and show no
signs of “burn by” (no gaps/spaces). If ok, proceed with checkout.