Summary

Air Conditioning Control Head Diagnostics

B. Turn the A/C blower-ON.

C. Set HVAC selector to Defrost Mode.
Yes:Blend door operates

correctly.Reassemble unit to run and retest for

operator concern.
D. Remove the fuse boxcover and remove the 5 Amp HVAC fuse (Battery to HVAC Control Head)(ProStar position is F1-B).

9

E. Wait approximately 30 seconds then reinstall the fuse.

F. You should hear the doors recalibrate by moving from one extreme position to the other.
No:Go to step 10
Note ­Do not operate the control head during the recalibration.

G. Start vehicle and check for correct operation of all modes and temperature.

all modes work correctly?

Step Do

Action
Decision
Blend Door Actuator Signal

A. Disconnect harness connector from blend door actuator.

B. Turn the ignition Key-On.
Yes: Go to step 12
C. Turn the A/C blower­ON.

10
D. Set HVAC selector to A/C MAX Mode.

E. Connect a test light between harness Pin-A and Pin-B.

F. Move temperature switch through ALL settings while observing the test light.
Does the test light illuminate in all switch positions?

(If using a DMM, Pin-A to Pin-B spec is 12V +/- 1.5)
Step Action
Blend Door Actuator Circuits

A. Inspect circuit A74B (connector 1200 Pin-B11, to connector 2010 Pin-C, to blend door actuator Pin-B).

11
No: Go to Step 11
Decision
Yes: Repair as needed. After repairs are

complete, reassemble unit and retest for

operator concern.
B. Inspect circuit A74C (connector 1200 Pin-B12, to connector 2010 Pin-D, to blend door actuator Pin-A).
Are circuits open or shorted?
Step Action
Blend Door Movement

A. Remove blend door actuator from interior module. Connect the harness connector to the actuator.
No: Replace control head. Reassemble unit and retest

for operator concern.
Decision
Yes: Reinstall blend door actuator, plug in

harness

connector, and then go to step 13.
B. Turn the ignition Key-ON.

C. Turn the blower­ON.

12
D. Set HVAC selector to A/C MAX Mode.

E. Move temperature switch through ALL settings while observing the actuator movement.
No: door binds or sticks: disassemble interior module

and repair as needed. After repairs are complete,

reassemble unit and retest for operator concern.
F. Move the blend door by hand through its full range of movement.
Does both the actuator respond to the control head signals and the door move freely?
Step Action
No: actuator does not function: replace actuator.

Reassemble unit and retest for operator concern.
Decision

Yes:Check Sealing around heater core
13
Heater Core Sealing
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IK1900226 ­ Air Conditioning Control Head Diagnostics
C. Start the engine and raise the idle speed to 1500 rpm.
Page 6 of 9
for placement. Remove blower scroll housing, and

heater core if required, to reposition seal around heater

core.
D. Turn HVAC control switch to NORM.

E. Turn Blower to highest speed and Temperature Control to coldest temp
Note:If vehicle has a manual coolant shut-off valve in

the heater core circuit, verify it is in the off position.
F. Insert thermometer into left side passenger dash vent. Do not allow thermometer to touch duct.

G. Open windows and close both cab doors.

H. After cab temperature stabilizes, record temperature.
After repairs are complete, reassemble unit and retest

for operator concern.

No:System is working correctly. Reassemble unit and

retest for operator concern.
I. Remove both pair of pinch-off pliers.
Is duct temperature correct until pliers are removed?
Step Action
Decision
Mode Control Door Recalibration

A. Turn the ignition Key­On.
Yes: Mode control operates correctly.
B. Turn the blower ON.

C. Set HVAC selector to Defrost Mode.
14
D. Remove the fuse box cover. Remove the 5 Amp fuse from

Battery to HVAC Control Head (ProStar position is F1-B).

E. Wait approximately 30 seconds then reinstall the fuse.

F. You should hear the doors recalibrate by moving from one

extreme position to the other.

Note: Do not operate the control head during the recalibration.
No: Go to step 15.
G. Start vehicle and check for correct operation of all modes and temperature.

Do all modes work correctly?
Step Action
Mode Door Actuator Signal
Decision
Yes: Go to step 17.
A. Disconnect harness connector from mode door actuator.

B. Turn ignition Key-On.

15
C. Turn blower ON

D. Set HVAC selector to A/C MAX Mode.

E. Connect a test light between harness Pin-A and Pin-B.

F. Move mode switch through ALL settings while observing the test light.

Does the test light illuminate in all switch positions?

(If using a DMM, pin-A to Pin-B spec is 12V +/- 1.5)
Step Action
No: Go to step 16.
Decision
Yes: Repair as needed. After complete,

reassemble unit and retest.

Mode Door Actuator Circuits

16
A. Inspect circuit A74 (connector 1200 Pin-B9 to connector 2010 Pin-A to mode actuator Pin-B).

B. Inspect circuit A74A (connector 1200 Pin-B10 to connector 2010 Pin-B to mode actuator Pin-A).

Are circuits open or shorted?
No: Replace control head.

Reassemble unit and retest.
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IK1900226 ­ Air Conditioning Control Head Diagnostics
Step Action
Page 7 of 9
Decision
Yes: system is functioning correctly.

Mode Door Movement

A. Remove mode door actuator from interior module. Connect the harness connector to the actuator.

B. Turn ignition Key-On.

C. Turn blower ON.
No: door binds or sticks: repair interior module as

needed. After repairs are complete, reassemble unit

and retest for operator concern
D. Move mode switch through ALL settings while observing the actuator movement.

17

E. Move the mode door by hand through its full range of movement.
Does both the actuator respond to the control head signals and thedoor move freely?

E. Move temperature switch through ALL settings while observing the actuator movement.

F. Move the blend door by hand through its full range of movement.
No: actuator does not function: Replace actuator.

Reassemble unit and retest for operator concern.
Does both the actuator respond to the control head signals and the door move freely?
Step Action
Decision
Recirculation Door Recalibration

A. Turn ignition Key­On.

B. Turn blower ON.

C. Set HVAC selector to Defrost Mode.
Yes: Recirculation Door operates correctly.

Reassemble unit and retest for operator

concern.
D. Remove the fuse box cover. Remove the 5 Amp fuse from Battery to HVAC Control Head (ProStar position is F1-B).

18

E. Wait approximately 30 seconds then reinstall the fuse.

F. You should hear the doors recalibrate by moving from one extreme position to the other.

Note: Do not operate the control head during the recalibration.

G. Start vehicle and check for correct operation of all modes and temperature.

Do all modes work correctly?
Step Action
No: Go to step 19.
Decision
A. Disconnect harness connector from recirculation door actuator.

B. Turn ignition Key-On.
Yes: Leave recirculation door actuator harness

unplugged and go to step 21.
C. Turn blower ON.

19
D. Set HVAC selector to A/C MAX Mode.

E. Insert a test light between Pin-A and Pin-B of the recirculation door harness.

F. Move mode switch from MAX to NORM.

Does test light illuminate brightly in MAX?

(If using a DMM, pin-A to Pin-B spec is 12V +/- 1.5)
No: Leave recirculation door actuator harness

unplugged and go to step 20.
Recirculation Door Actuator Signal
Step Action

20
A. Inspect circuit A74D (connector 1200 Pin-B1 to connector 2010 Pin-E to mode actuator

Pin-A).
Decision

Yes: Repair as needed. Reassemble unit and

retest for operator concern.
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IK1900226 ­ Air Conditioning Control Head Diagnostics
Page 8 of 9
No: Replace control head. Reassemble unit and retest

for operator concern.
B. Inspect circuit A74E (connector 1200 Pin-B2 to connector 2010 Pin-F to mode actuator

Pin­F).

Are circuits open or shorted?

Recirculation Door Actuator Circuits
Step Action
Decision
Yes: Recirculation door is functioning correctly.

Recirculation Door Actuator Movement

A. Remove recirculation door actuator from interior module. Connect the harness connector to the actuator.

B. Turn ignition Key-ON.

21

C. Turn blower ON.

D. Move mode switch from NORM to MAX A/C while observing the actuator movement.
No: Door binds or sticks: repair interior module as

needed. Reassemble unit and retest for operator

concern.
E. Move the recirculation door by hand through its full range of movement.

Does both the actuator respond to the control head signals and thedoor move freely?
Step Action
No: actuator does not function: Replace actuator.

Reassemble unit and retest for operator concern.
Decision

Step C: does not illuminate the test light

brightly:

If 10A HVAC fuse is good, check circuit A73A

for open or high resistance.

After repairs are complete, reassemble unit

and retest.
Control Head Power

A. Turn ignition Key-ON.
Step D: does not illuminate the test light brightly:

Check circuit A74G and A11-GCA for open or high

resistance (Connector 1200) Pin-B6 to Left Side

Dash Mounted Dual Post GND Plate).
B. Connect a 12V test light between a good ground and Pin-A1 of the A/C control head harness connector (1200).

After repairs are complete, reassemble unit and retest

C. Wiggle 10A fuse F4­L while watching test light to check for loose/ intermittent fuse connection.

Step F: does not illuminate the test light

22
D. Connect a 12V test light between Pin-A1 and B6 of the 1200 connector and monitor test light.
brightly:
E. Connect a 12V test light between a good ground and Pin-A2 of the A/C control head harness connector (1200).
If 5A HVAC fuse is good, check circuit A75D

for open or high resistance.
F. Wiggle 5A fuse F1­B while watching test light to check for loose/ intermittent fuse connection.

G. Connect a 12V test light between Pin-A2 and B6 of the 1200 connector and monitor test light
Which of the following steps does not illuminate the test light brightly: Step C, D, F, or G?
After repairs are complete, reassemble unit

and retest

Step G: does not illuminate the test light

brightly:

Check circuit A74G and A11-GCA for open or

high resistance (Connector 11200 Pin-B6 to

Left Side Dash Mounted Dual Post GND

Plate).

After repairs are complete, reassemble unit

and retest.
WARRANTY INFORMATION

NOTE: There are multiple noun groups that the diagnostic time could be charged to.
WARRANTY CLAIM CODING:
:
Group 19000 -Truck Air Conditioner

Noun:
Multiple Nouns - Code to repair made
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IK1900226 ­ Air Conditioning Control Head Diagnostics
Page 9 of 9
Warranty Coding Manual
STANDARD REPAIR TIMES:

DIAGNOSTICS

Step
Description
Models
Hours
1­23
A/C CONTROL HEAD DIAGNOSIS
All
Varies Per

Model
Link to the Standard Repair Time Manual: Click Here
Hide Details
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TSB/Document ID: IK1900226

Replacement Service Bulletin Number:

MFR Communication Date: 2017-05-04

MFR Internal Campaign ID/Software Version:

Communication Type: Service Bulletin/Repair Instructions

NHTSA Components: EQUIPMENT:APPLIANCE:AIR CONDITIONER

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