Vintage Air 751170 User manual

1967-72 Chevy Pickup
without Factory Air
751170
901149 REV D 7/30/14, INST 67-72 CHEVY PICKUP wo AC EVAP KIT PG 1 OF 24
an ISO 9001:2008 Registered Company
18865 Goll St. San Antonio, TX 78266 ph: 210-654-7171 fax: [phone]

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901149 REV D 7/30/14, INST 67-72 CHEVY PICKUP wo AC EVAP KIT PG 2 OF 24
Table of Contents
1. Cover
2. Table of Contents
3. Packing List/Parts Disclaimer
4. Information Page
5. Wiring Notice
6. Engine Compartment
Figure 1
7. Condenser Assembly, Compressor & Bracket, Passenger
Compartment
Figure 2
8. Defrost Duct and Louver Installation
Figures 3, 3a & 3b
9. Fresh Air Cap and Firewall Cover Installation, Bracket and Evaporator
Hardline Installation
Figures 4 & 5
10. Bracket and Evaporator Hardline Installation (Cont.)
Figure 6
11. Evaporator Installation
Figures 7 & 7a
12. Drain Hose Installation, Lubricating O-rings, A/C Hose Installation
Figures 8 & 9
13. Heater Hose & Heater Control Valve Installation
Figure 10
14. A/C & Heater Hose Routing
Figure 11
15. Final Steps
Figures 12 & 12a
16. Control Panel & Duct Hose Routing
Figure 13
17.
Wiring Diagram
18.
Gen IV Wiring Connection Instructions
19. Operation of Controls
20. Tr
oubleshooting Information
21. Tr
oubleshooting Information (Cont.)
22. Driver/Passenger Side Louver Template
23. Center Louver Template
24. Evaporator Kit Packing List

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901149 REV D 7/30/14, INST 67-72 CHEVY PICKUP wo AC EVAP KIT PG 3 OF 24
Evaporator Kit (751170)
1
Accessory Kit
791170
2
No. Qty. Part No. Description
NOTE: Images may not depict actual parts and quantities.
Refer to packing list fo r actual parts and quantities.
Gen IV 3-Vent
Evaporator Sub Case
w/ 204 ECU
744005
Gen IV 3-Vent Evaporator Sub Case w/ 204 ECU
Accessory Kit 67-72 Chevy Pickup without A/C
1.
2.
1
1
744005
791170
** Before beginning installation, open all packages and check contents of shipment.
Please report any shortages directly to Vintage Air within 15 days. After 15 days,
Vintage Air will not be responsible for missing or damaged items.
Packing List

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901149 REV D 7/30/14, INST 67-72 CHEVY PICKUP wo AC EVAP KIT PG 4 OF 24
Use of Any Other Refrigerants Will Void All Warranties of the Air
Conditioning System and Components. Use of the Proper Type and
Amount of Refrigerant Is Critical to Proper System Operation. Vintage
Air Recommends Our Systems Be Charged By Weight With a Quality
Charging Station or Scale.
Service Info:
Safety Switches:
Important Notice—Please Read
Attention: The following system components are capped: Compressor, evaporator, condenser & drier.
Caps may be under pressure with dry nitrogen. Be careful removing caps. Do not remove caps prior to
installation. Removing caps prior to installation will cause components to collect moisture and lead to
premature failure and reduced performance.
Evacuate the system for 35-45 minutes with system components (Drier, compressor, evaporator and
condenser) at a temperature of at least 85°F. On a cool day, the components can be heated with a heat
gun OR by running the engine with the heater on before evacuating. Leak check and charge to
specifications.
For Maximum System Performance, Vintage Air Recommends the Following:
Heater hose may be purchased from Vintage Air (Part# 31800-VUD) or your local parts retailer.
Routing and required length will vary based on installer preference.
Vintage Air Systems Are Designed to Operate With R134a
Refrigerant Only! Use of Any Other Refrigerants Is a Fire Hazard and
Could Damage Either Your Air Conditioning System or Your Vehicle.
Refrigerant Capacity for Vintage Air Systems:
(For other systems, consult manufacturer’s guidelines)
R134a System
Charge with 1.8 lbs. (1 lb., 12 oz.) of refrigerant.
Lubricant Capacities:
New Vintage Air-supplied Sanden Compressor: No additional oil needed (Compressor is
shipped with proper oil charge).
All Other Compressors: Consult manufacturer (Some compressors are shipped dry and will
need oil added).
Your Vintage Air system is equipped with a binary pressure safety switch. A binary switch disengages
the compressor clutch in cases of extreme low pressure conditions (Refrigerant Loss) or excessively
high head pressure (406 PSI) to prevent compressor damage or hose rupture. A trinary switch
combines Hi/Lo pressure protection with an electric fan operation signal at 254 PSI, and should be
substituted for use with electric fans. Compressor safety switches are extremely important since an
A/C system relies on refrigerant to circulate lubricant.
Heater Hose (Not Included With This Kit):
To ensure a watertight seal between the passenger compartment and the vehicle exterior, for all
bolts passing through the cowl and/or firewall, Vintage Air recommends coating the threads with
silicone prior to installation.
Bolts Passing Through Cowl and/or Firewall:

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901149 REV D 7/30/14, INST 67-72 CHEVY PICKUP wo AC EVAP KIT PG 5 OF 24
Important Wiring Notice—Please Read
Some Vehicles May Have Had Some or All of Their Radio Interference Capacitors Removed.
There Should Be a Capacitor Found At Each of the Following Locations:
1. On the positive terminal of the ignition coil.
2. If there is a generator, on the armature terminal of the generator.
3. If there is a generator, on the battery terminal of the voltage regulator.
Most alternators have a capacitor installed internally to eliminate what is called “whining” as
the engine is revved. If whining is heard in the radio, or just to be extra cautious, a radio
interference capacitor can be added to the battery terminal of the alternator.
It is also important that the battery lead is in good shape and that the ground leads are not
compromised. There should be a heavy ground from the battery to the engine block, and
additional grounds to the body and chassis.
If these precautions are not observed, it is possible for voltage spikes to be present on the
battery leads. These spikes come from ignition systems, charging systems, and from
switching some of the vehicle’s other systems on and off. Modern computer-operated
equipment can be sensitive to voltage spikes on the power leads, which can cause unexpected
resets, strange behavior, and/or permanent damage.
Vintage Air strives to harden our products against these types of electrical noise, but there is
a point where a vehicle’s electrical system can be degraded so much that nothing can help.
Radio interference capacitors should be available at most auto and truck parts suppliers. They
typically are cylindrical in shape, a little over an inch long, a little over a half inch in diameter,
and they have a single lead coming from one end of the cylinder with a terminal on the end of
the wire, as well as a mounting clip which is screwed into a good ground on the vehicle. The
specific value of the capacitance is not too significant in comparison to ignition capacitors that
are matched with the coil to reduce pitting of the points.
Care must be taken, when installing the compressor lead, not to short it to ground.
The compressor lead must not be connected to a condenser fan or to any other
auxiliary device. Shorting to ground or connecting to a condenser fan or any other
auxiliary device may damage wiring, the compressor relay, and/or cause a
malfunction.
When installing ground leads on Gen IV systems, the blower control ground and ECU
ground must be connected directly to the negative battery post.
For proper system operation, the heater control valve must be connected to the
ECU.
•
•
•

6
901149 REV D 7/30/14, INST 67-72 CHEVY PICKUP wo AC EVAP KIT PG 6 OF 24
FIGURE 1OEM Heater
Blower
Assembly
Engine Compartment
1.
2.
3.
NOTE: Before starting the installa tion, check the function of the vehicle (horn, lights, etc.) for proper
operation, and study the instructions, illustrations & diagrams.
Perform the Following:
Disconnect battery.
Drain and remove radiator (retain).
Remove heater blower assembly and OEM heater hoses (discard).
NOTE: To remove the OEM heater blower assembly (under hood) and the air distribution system
(under dash), the factory manual recommends that the right inner fender be removed for accessibility.
Figure 1

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901149 REV D 7/30/14, INST 67-72 CHEVY PICKUP wo AC EVAP KIT PG 7 OF 24
OEM Heater Assembly
& Related Ducting
OEM Defrost
Duct Assembly
Control
Panel
Radio
Glove Box
Door
Assembly and Installation
Refer to separate instructions included with the condenser kit to install the condenser.
Binary switch installation (Refer to condenser instructions).
1.
2.
Compressor and Brackets
Refer to separate instructions included with the bracket kit to install the compressor and bracket.1.
Passenger Compartment
1.
2.
3.
4.
Perform the Following:
Remove the glove box door (retain) and glove box (discard).
Disconnect all wires and cables from control panel and radio.
Remove all hoses and ducting from defrost ducts (See Figure 2, below).
Remove OEM heater assembly.
Figure 2
Condenser

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901149 REV D 7/30/14, INST 67-72 CHEVY PICKUP wo AC EVAP KIT PG 8 OF 24
Hose
Adapter
Ball
Louver
49053-VUL
Dash
Passenger Side
Oval Defrost
Adapter
49167-VCI
(2) S-clips
(2) S-clips
Driver Side
Round Defrost
Adapter
49168-VCI
(2) 1/4-20 Nuts
w/ Star Washers
(2) 1/4” Flat
Washers
Dash
OEM Defrost
Ducts
Defrost Duct
and Louver Installation
1.
2.
3.
Install S-clips on defrost duct hose adapters, and attach to OEM defrost ducts as shown in Figure 3, below.
Install center louver into dash as shown in Figure 3b, below. Use dimensions provided on Page 23. NOTE:
Center louver may need to be tapped to 1/4-20 to accept studs.
Install driver/passenger side louvers into dash as shown in Figure 3a, below. Use template provided on Page
22.
(2) 1/4-20 X 1 ¾”
Studs
NOTE: Studs, nuts and washers are
packaged in bag with heater control
valve.
Figure 3
Figure 3a
Figure 3b

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901149 REV D 7/30/14, INST 67-72 CHEVY PICKUP wo AC EVAP KIT PG 9 OF 24
(2)1/4-20 X 1/2”
Hex Bolts
Front
Evaporator
Bracket
644080
Silicone
Back Side
of Fresh Air
Cap
Back Side
of Firewall
Cover
648218
1/4-20 X 1”
Bolt
Silicone
1/4” Flat
Washer 1/4-20 X 1”
Bolt
1/4-20 X 1”
Bolt
Drill
9/32” Hole
Drill
9/32” Hole
1/4” Flat
Washer 1/4” Nut w/
Star Washer
1/4” Nut w/
Star Washer
OEM
Hole
(6) #14 X 3/4”
Sheet Metal
Screws
Large
Grommet
33137-VUI
Grommet
33135-VUI
3/8”
Grommet
33144-VUI
1/4” Flat
Washer
Fresh Air
Cap
OEM
Hole
Fresh Air Cap
& Firewall Cover Installation
1.
2.
3.
4.
5.
6.
7.
Apply a 1/4” bead of silicone around the back side of the fresh air cap as shown in Figure 4, below.
Attach fresh air cap to firewall using a 1/4-20 x 1” bolt and washer (See Figure 4, below).
Apply a 1/4” bead of silicone around the back side of the firewall cover as shown below.
Install firewall cover onto firewall using (2) 1/4-20 x 1” hex bolts, (2) flat washers and (2) 1/4” nuts with star
washers in the OEM holes as shown below.
Use firewall cover as a template to drill (6) 3/16” holes in firewall, and then secure using #14 x 3/4” sheet
metal screws as shown below.
Using the firewall cover as a template, drill (2) 9/32” holes in the firewall as shown below.
Install grommets as shown below.
Bracket & Evaporator Hardline Installation
Figure 4
Figure 5
1.
2.
3.
On a workbench, install evaporator rear
bracket using (4) 1/4-20 x 1/2” hex
bolts.
Install hardlines with properly lubricated
O-rings (See Figure 9, Page 12, and
Figure 6, Page 10). NOTE: Wrap the
#10 fitting connections with press
tape (See Figure 6, Page 10).
Install evaporator front bracket onto
evaporator using (2) 1/4-20 x 1/2” hex
bolts, and tighten as shown in Figure 5,
below.

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901149 REV D 7/30/14, INST 67-72 CHEVY PICKUP wo AC EVAP KIT PG 10 OF 24
Rear
Evaporator
Bracket Assembly
644073
(2) 1/4-20 x 1/2”
Hex Bolts
(2) 1/4-20 x 1/2”
Hex Bolts
#6 Liquid Line
095002
Twist With
This
Wrench
Lubricate O-ring
(See Figure 9,
Page 12)
Hold With
This Wrench
Heater Line
(Evaporator to Water Pump)
095004
ECU Module
#10 O-ring
NOTE: After Installing
#10 Suction Line, Wrap
All Exposed Metal
(Fittings & Tube)
With Supplied Press Tape.
#10 O-ring
#10 Suction
Line
095003
#6 Liquid Line
095002
Press Tape
Heater Line
(Evaporator to Intake)
095005
#6
O-ring
Bracket & Evaporator
Hardline Installation (Cont.)
Figure 6

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901149 REV D 7/30/14, INST 67-72 CHEVY PICKUP wo AC EVAP KIT PG 11 OF 24
Inner Cowl
Drill (2)
3/16” Holes
(2)#14 x 3/4
”
Sheet Metal
Screws
1/4-20 x 1”
Hex Bolt
1/4-20 x 1”
Hex Bolt
Flat
Washer
1/4”
Flat
Washer
1/4” Nut w/
Star Washer
View From
Passenger Side,
Inside of Cab
Evaporator Installation
1.
2.
3.
Lift evaporator unit up under the dashboard, and secure loosely to the firewall using (2) 1/4-20 x 1” hex bolts,
(2) flat washers and (2) 1/4” nuts with star washers (See Figure 7, below). NOTE: To ensure proper
drainage, it is very important that the evaporator is level, both left-to-right and fore-aft. Check for
level on the flat portions of the case around the drain, block the unit up, and then drill holes for
front bracket screws.
Secure the front evaporator mounting bracket to the cowl using (2) #14 x 3/4” hex sheet metal screws (See
Figure 7a, below).
Verify that the evaporator unit is level and square to the dash, and then tighten all mounting bolts. NOTE:
Tighten the bolt on firewall first, and then the front mounting bracket.
Figure 7
Figure 7a

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901149 REV D 7/30/14, INST 67-72 CHEVY PICKUP wo AC EVAP KIT PG 12 OF 24
Evaporator
Case
1”
Drain
Hose
1”
Drain Hose Installation
1.
2.
3.
Locate evaporator drain on bottom of
evaporator case.
In line with drain, lightly make a mark on the
firewall. Measure 1” down and drill a 5/8”
hole through the firewall.
Install drain hose to bottom of evaporator unit
and route through firewall. Install 1/2” 90°
drain elbow onto drain hose.
Figure 8
A/C Hose Installation
Standard Hose Kit:
Modified A/C Hose Kit:
Locate the #8 compressor A/C hose. Lubricate (2) #8 O-rings (See Figure 9, above) and connect the 135°
female fitting with 134a service port to the #8 discharge port on the compressor. Route the straight female
fitting to the #8 condenser hardline coming through the core support (See Figure 11, Page 14). Tighten each
fitting connection as shown.
Locate the #10 compressor A/C hose. Lubricate (2) #10 O-rings (See Figure 9, above) and connect the #10
135° female fitting with 134a service port to the #10 suction port on the compressor. Route the 90° female
fitting to the #10 evaporator (See Figure 10, Page 13, and Figure 11, Page 14). Tighten each fitting connection
as shown.
Locate the #6 evaporator A/C hose. Lubricate (2) #6 O-rings (See Figure 9, above) and connect the straight
female fitting to the #6 condenser hardline coming through the core support. Route the 90° female fitting to
the #6 evaporator (See Figure 10, Page 13, and Figure 11, Page 14). Tighten each fitting connection as shown.
1.
2.
3.
1.
Figure 9
O-ring Installs
Over Male Insert
to Swaged Lip
O-ring
#6 O-ring
#8 O-ring #10 O-ring
O-ring
Supplied Oil
for O-rings
Male
Insert Female Nut
Hold With
This Wrench
Twist With
This Wrench
Lubricating O-rings
For a proper seal of fittings: Install supplied
O-rings as shown, and lubricate with supplied
oil.
NOTE: Standard torque specifications:
#6: 11 to 13 ft-lb.
#8: 15 to 20 ft-lb.
#10: 21 to 27 ft-lb.
Refer to separate instructions included with modified hose kit.

13
901149 REV D 7/30/14, INST 67-72 CHEVY PICKUP wo AC EVAP KIT PG 13 OF 24
#10 Suction
Line
O-rings
Heater
Hose NOTE: Flow Direction Follows
Molded Arrow on Valve.
Liquid
Line
FROM HTR CNTRL VLV
TO EVAPORATOR
FROM EVAPORATOR
TO WATER PUMP
FROM INTAKE
MANIFOLD
Heater Hose and
Heater Control Valve Installation
Route heater hose from water pump to the heater line coming through the firewall as shown in Figure 10,
below. Secure using hose clamps. NOTE: A small amount of silicone spray will ease heater hose
installation.
Route heater hose from the intake to the heater line coming through the firewall as shown below. NOTE:
Install heater control valve in line with intake manifold (pressure side) heater hose, and secure
using hose clamps as shown. Also note proper flow direction.
Hose should protrude through the firewall cover slightly to close the gap between the aluminum line and the
firewall cover. Seal any remaining gap with RTV silicone.
1.
2.
3.
Figure 10

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901149 REV D 7/30/14, INST 67-72 CHEVY PICKUP wo AC EVAP KIT PG 14 OF 24
FROM INTAKE
MANIFOLD
Figure 11
#6 Hose
096002
Tie Wrap
#8 Discharge
Hose
096001
#6 Cond/Drier
Hardline
35056-LCG
NOTE: Vintage Air Systems Require
(2) 5/8” Hose Nipples (Not Supplied).
5/8” Heater
Hose
FROM EVAPORATOR
TO WATER PUMP
Compressor
Safety Switch (Binary Type)
Screw-On Drier (Refer To
Condenser Instructions)
A/C & Heater Hose Routing
#10 Suction
Hose
096003
#8 Condenser/
Comp. Hardline
095007
#6 Drier/Core
Support
Hardline
095006
NOTE: Flow Direction Follows Molded Arrow on Valve.
Heater Hose
(Heater Control
Valve/Intake)
From Heater Control
Valve
to Evaporator

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901149 REV D 7/30/14, INST 67-72 CHEVY PICKUP wo AC EVAP KIT PG 15 OF 24
Glove Box
496067
Final Steps
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
Install duct hoses as shown in Figure 13, Page 16.
Route A/C wires (12 volt/ground/binary switch/heater valve) through 3/8” grommet as shown in Figure 12,
below.
Install control panel assembly.
Plug the wiring harnesses into the ECU module on the sub case as shown in Figure 13, Page 16 (Wire according
to wiring diagram on Pages 17 and 18).
Install new glove box using OEM screws (See Figure 12a, below).
Install glove box door.
Reinstall all previously removed items, including inner fender.
Fill radiator with at least a 50/50 mixture of approved antifreeze and distilled water. It is the owner's responsibility
to keep the freeze protection at the proper level for the climate in which the vehicle is operated. Failure to follow
antifreeze recommendations will cause heater core to corrode prematurely and possibly burst in A/C mode and/or
freezing weather, voiding your warranty.
Double check all fittings, brackets and belts for tightness.
Vintage Air recommends that all A/C systems be serviced by a certified automotive air conditioning technician.
Evacuate the system for a minimum of 45 minutes prior to charging, and perform a leak check prior to servicing.
Charge the system to the capacities stated on Page 4 of this instruction manual.
See Operation of Controls procedures on Page 19.
Figure 12a
Figure 12
Grommet
33144-VUI
Wiring Harness
(12 Volt/Ground/Binary Switch)
Wiring Harness
(Heater Control Valve)

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901149 REV D 7/30/14, INST 67-72 CHEVY PICKUP wo AC EVAP KIT PG 16 OF 24
Plug
From
Control
Wiring
Harness
232002-VU
A
Plug
From
Wiring
Harness
232001-VUR
Passenger Side
Louver
2 ½” X 36”
Driver Side
Louver
2 ½” X 48”
Center
Louver
2 ½” X 18”
Passenger Side
Defrost Duct
2” X 12”
Driver Side
Defrost Duct
2” X 24”
Control Panel
and Duct Hose Routing
Figure 13

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901149 REV D 7/30/14, INST 67-72 CHEVY PICKUP wo AC EVAP KIT PG 17 OF 24
WHT/GRN
WHT/YEL
WHT/RED
RED
WHT
BACKLIGHT NEG
FAN WIPER
MODE WIPER
TEMP WIPER
5V-SW
GND
BACKLIGHT POS
AC ANNUNCIATOR
PRE-WIRED
GEN IV WIRING DIAGRAM
REV D, 5/6/2014
GEN IV ECU
PROGRAM
Wiring Diagram
TEMP
MODE
FAN
A/C
(IF USED)
232007-VUR
232002-VUA
** CIRCUIT
BREAKER
30 AMP
*** WIDE OPEN
THROTTLE
SWITCH
(OPTIONAL)
* DASH LAMP
(IF USED)
Dash Lamp Is Used Only With Type 232007-VUR Harness.
Warning: Always Mount Circuit Breaker As Close to the Battery As Possible. (NOTE: Wire Between
Battery and Circuit Breaker Is Unprotected and Should Be Carefully Routed to Avoid a Short
Circuit).
Wide Open Throttle Switch Contacts Close Only at Full Throttle, Which Disables A/C
Compressor.
JF8
BLK
ORA
TAN
VIEWED FROM WIRE SIDE
•
•
•
HEATER
CONTROL VALVE

18
901149 REV D 7/30/14, INST 67-72 CHEVY PICKUP wo AC EVAP KIT PG 18 OF 24
RED
CIRCUIT BREAKER
30 AMP
+
+
-
BLACK
RED
WHITE
RED
CHASSIS GROUND
A/C
COMPRESSOR
RELAY
Ignition Switch:
Dash Light:
NOTE:
MOUNT RELAY
IN DESIRED
LOCATION
UNDER DASH
GREEN
FIREWALL
BLUE
BLUE
RED
&
WHITE
VIOLET
(IGNITION HOT
TERMINAL)
IGNITION
SWITCH
DASH BACK LIGHT+0-12v
TAN
GRAY
BLUE
WHITE
WHITE
RED
RED
WHITE
COMPRESSOR
BATTERY
NOTE: CONNECT WHITE
WIRES DIRECTLY TO
(-) BATTERY TERMINAL
BAT
RUN
12V
RED
GREEN
RED
RED
BLUE
LATCH
BLACK
BINARY
SAFETY
SWITCH
YELLOW
ORANGE
WIRING
HARNESS
Violet 12V Ign Switch Source (Key On
Accessory) Position Must Be Switched.
Tan Wire Used Only With Vintage Air
Supplied Control Panel With LED Back
Light.
Binary: Connect As Shown (Typical
Compressor Wiring). Be Sure
Compressor Body Is Grounded.
Trinary Switch: Connect According To
Trinary Switch Wiring Diagram.
Install With Servo Motor Facing Down,
As Shown. Note Flow Direction Arrow
Molded Into Valve Body, And Install
Accordingly.
White Must Run To (-) Battery. Red May
Run To (+) Battery Or Starter. Mount
Circuit Breaker As Close to Battery As
Possible.
Heater Control Valve:
Binary/Trinary & Compressor:
Circuit Breaker/Battery:
CONTROL
WIRING
HARNESS
NOTE:
YELLOW & ORANGE
COMING FROM
HARNESS ARE NOT
USED.
WIRING
HARNESS
GRAY WIRE IS USED FOR
PROGRAMING CONTROLS
IF APPLICABLE
WIRING
HARNESS
Gen IV Wiring
Connection Instruction
HEATER
CONTROL VALVE
WARNING:
ALWAYS MOUNT CIRCUIT BREAKER
AS CLOSE TO THE BATTERY AS POSSIBLE.
(NOTE: WIRE BETWEEN BATTERY AND
CIRCUIT BREAKER IS UNPROTECTED
AND SHOULD BE CAREFULLY ROUTED
TO AVOID A SHORT CIRCUIT).
NOTE: HEATER CONTROL
VALVE CONNECTION AND
CHASSIS GROUND MAY BE
LOCATED ON EITHER SIDE
OF THE FIREWALL. ENSURE
CONNECTOR IS LATCHED
FIRMLY.

19
901149 REV D 7/30/14, INST 67-72 CHEVY PICKUP wo AC EVAP KIT PG 19 OF 24
Operation of Controls
Adjust to desired
speed.
Blower Speed
Adjust to desired
speed.
Adjust to desired
mode position
(DASH position
recommended).
Adjust to desired
speed.
Adjust to DEFROST position for maximum defrost, or
between FLOOR and DEFROST positions for a bi-level
blend (Compressor is automatically engaged).
Adjust to desired
temperature.
For A/C operation, adjust to
coldest position to engage
compressor (Adjust between
HOT and COLD to reach
desired temperature).
A/C Operation
Heat Operation
Defrost/De-fog Operation
On Gen IV systems with three lever/knob controls, the temperature control toggles between heat and A/C
operations. To activate A/C, move the temperature lever/knob all the way to cold and then back it off to the desired
vent temperature. For heat operation, move the temperature lever/knob all the way to hot and then adjust to the
desired vent temperature. The blower will momentarily change speed, each time you toggle between operations, to
indicate the change. NOTE: For proper control panel function, refer to control panel instructions for
calibration procedure.
Blower Speed
Blower Speed
This lever/knob controls
blower speed, from
OFF to HI.
This lever/knob controls
the mode positions,
from DASH to FLOOR
to DEFROST, with a
blend in between.
This lever/knob controls
the temperature,
from HOT to COLD.
Blower Speed
Mode Control
Temperature Control
Blower
Speed
Temperature
Control
Mode
Control
Temperature Control
Temperature Control
Temperature Control
Mode Control
Mode Control
Mode Control
For maximum heating, adjust
to hottest position (Adjust
between HOT and COLD to
reach desired temperature).
Adjust to desired
mode position
(FLOOR position
recommended).
HEAT
DEF
AIR FAN
(DASH) (FLOOR) (DEFROST)
HEAT
DEF
AIR FAN
HEAT
DEF
AIR FAN
HEAT
DEF
AIR FAN

20
901149 REV D 7/30/14, INST 67-72 CHEVY PICKUP wo AC EVAP KIT PG 20 OF 24
Symptom Condition Checks Actions Notes
Blower stays on high speed when ignition is on.
1a.
No other functions work.
Check for damaged pins or wires in control head plug.
Verify that all pins are inserted into plug. Ensure that no pins are bent or damaged in ECU.
Check for damaged ground wire (white) in control head harness.
Verify continuity to chassis ground with white control head wire at various points.
Loss of ground on this wire renders control head inoperable.
All other functions work. Check for damaged blower
switch or potentiometer and associated wiring.
Blower stays on high speed when ignition is on or off.
Unplug 3-wire BSC control connector from ECU. If blower shuts off, ECU is either improperly wired or damaged.
Be sure the small, 20 GA white ground wire is connected to the battery ground post. If it is, replace the ECU.
Unplug 3-wire BSC control connector from ECU. If blower stays running, BSC is either improperly wired or damaged.
Check to ensure that no BSC wiring is damaged or shorted to vehicle ground. The BSC operates the blower by ground side pulse width modulation switching. The positive wire to the blower will always be hot. If the “ground” side of the blower is shorted to chassis ground, the blower will run on HI. Replace BSC (This will require removal of evaporator from vehicle).
No other part replacements should be necessary.
Compressor will not turn on (All other functions work).
2.
System is not charged. System must be charged for
compressor to engage. Charge system or bypass pressure switch.
Danger: Never bypass safety switch with engine running. Serious injury can result.
System is charged.
1b.
Troubleshooting Guide
Check for faulty A/C potentiometer or associated wiring (Not applicable to 3-pot controls).
Check for disconnected or faulty thermistor.
Check continuity to ground on white control head wire. Check for 5V on red control head wire.
Check 2-pin connector at ECU housing.
To check for proper pot function, check voltage at white/blue wire. Voltage should be between 0V and 5V, and will vary with pot lever position. Disconnected or faulty thermistor will cause compressor to be disabled. Red wire at A/C pot should have approximately 5V with ignition on. White wire will have continuity to chassis ground. White/ Blue wire should vary between 0V and 5V when lever is moved up or down.
3.
Compressor will not turn off (All other functions work).
Check for faulty A/C potentiometer or associated wiring. Check for faulty A/C relay.
Repair or replace pot/control wiring.
Replace relay.
See blower switch check procedure.