IK1900230 ­ Rear A/C Blows Warm Air

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IK1900230

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9/26/2014

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10/3/2014
Kevin
Kochanek

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Title : Rear A/C Blows Warm Air
Applies To : ProStar and LoneStar

CHANGE LOG
Please refer to the change log text box below for recent changes to this article:
10/2/2014 - Initial Article Release




DESCRIPTION
This document is supplemental to IK1900228 and addresses Rear A/C Blows Warm Air.

SYMPTOM(s)
Rear A/C Blows Warm Air.
Diagnostic Trouble Code(s) & Dashboard Indicator Light(s):
DTC/Light
Not Applicable

Description

Possible Causes:
•
•
•
•
•

Rear blend door actuator
Rear blend door or housing damage
Rear HVAC temperature sensor
Rear Thermal Expansion Valve (TXV)
Rear HVAC controller

Customer Observations or Concerns:
•
•
•
•

Malfunction Indicator Lamp (MIL)
No rear A/C control from sleeper
Rear A/C not blowing cold enough
No air flow through rear vent

SPECIAL TOOL(s) / SOFTWARE
Tool Description

Tool Number

Comments

Instructions

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IK1900230 ­ Rear A/C Blows Warm Air

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Diamond Logic Builder (DLB)
Tools Resource Center

SERVICE PARTS INFORMATION
Kit Description

Part Number

Quantity Required

Notes

Not Applicable

DIAGNOSTIC STEP(s)

To prevent property damage, personal injury, and / or death, read all safety instructions in
the "Safety Information" section of the Service Manual or Diagnostic Manual.

To prevent property damage, personal injury, and / or death, park vehicle on a hard, flat
surface, turn engine off, set parking brake, and install wheel chocks to prevent vehicle
from moving in either direction.

To prevent personal injury and / or death, make sure engine has cooled before removing
components.

The following procedures are ONLY VALID if A/C system is fully charged and A/C system checks in IK1900228 were performed.
When a failed circuit or component is detected, repair as needed and retest for original problem.

Step Action
Blend Door Operation:

Decision
Yes. Go to Step 5.

a. Turn ignition Key-ON.
b. Use Diamond Logic Builder (DLB) to command a rear HVAC Door Calibration.
c. Gain access to rear blend door actuator.
d. Sweep rear control panel temperature switch through all settings while monitoring blend door
actuator collar.
No. Go to Step 2.

#1
Does collar move through 45° of rotation?

Step Action

Decision

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IK1900230 ­ Rear A/C Blows Warm Air

Blend Door Actuator:

Page 3 of 5

Yes. Go to Step 4.

a. Turn ignition Key­OFF.
b. Disconnect blend door actuator connector (5212).
c. Turn ignition Key-ON.
d. Measure voltage at connector 5212 pin-5 to ground while operating rear control panel
temperature switch through all settings.
No. Go to Step 3.

#2
Does Step 2.d measure 10.5 ­ 13.5V?

Step Action
Blend Door Signal:

Decision
Yes. Replace rear HVAC
controller.

a. Turn ignition Key­OFF.
b. Disconnect rear HVAC controller connector (5210).
c. Check continuity of circuit H77TMA (connector 5210 pin-11 to connector 5212 pin-5) and
H77TFB (connector 5210 pin­9 to connector 5212 pin­7).
#3

Do both circuits have continuity?

Step Action
Blend Door Operation:

No. Repair circuits as needed.

Decision
Yes. Replace actuator. If system
still blows warm air, go to Step 5.

a. Turn ignition Key-OFF.
b. Remove blend door actuator from HVAC housing.
c. Check condition of actuator collar and blend door shaft.
d. Rotate blend door by hand to check for free movement.
#4

Does blend door operate freely and rotate through 45° of rotation?

Step Action
Rear HVAC Discharge Temp Setting:
a. Turn rear HVAC blower ON.

Do not allow thermometer to touch duct.
#5

No. Disassembly rear HVAC
housing as required to determine
blend door issue. Repair as
needed.

Decision
Yes. If rear A/C still blows warm
air, inspect refrigerant piping to
sleeper evaporator for restrictions
(look for cold spots in pipes) or
restricted or failed rear TXV.

No. Go to Step 6.

b. Insert a thermometer into rear HVAC discharge duct.
c. Start DLB.
d. "Watch" Rear_HVAC_Discharge_Temp_SettingSignal.
Does DLB value agree with measured duct temperature?

Step Action

Decision

#6

Yes. Go to Step 7.

Rear HVAC Temp Sensor Voltage:
a. Turn rear HVAC blower OFF.
b. Turn ignition Key-OFF.
c. Disconnect rear HVAC temperature sensor connector (5213).
d. Turn ignition Key-ON.

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IK1900230 ­ Rear A/C Blows Warm Air

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e. Measure voltage from rear HVAC Temp sensor connector 5213 pin-1 to pin-2.
No. Inspect for an open or shorted
circuit H77TSA (controller pin-13
to Temp sensor connector pin-1)
or circuit H77TSB (controller pin12 to Temp sensor connector pin2).

Is there 10.5 ­ 13.5V between pin­1 and pin­2?

Step Action

Decision

Temp Sensor Resistance:

Yes. Sensor circuit works
correctly.

a. Turn ignition Key-OFF.
b. Disconnect rear HVAC controller connector (5210).
c. Measure resistance from pin-12 to pin-13 of harness connector 5210.
d. Compare measured resistance and current temperature to Thermistor Cross Reference Table.
Is Step 7.c measurement correct for the temperature?

If rear A/C still blows warm air,
inspect refrigerant piping to
sleeper evaporator for
restrictions (look for cold spots in
pipes) or restricted or failed rear
TXV.

Thermistor Cross Reference Table.
NOMINAL
TEMP
TEMP
MIN 
MAX  (kohms)
(C°)
(F°)
(kohms)  (kohms)
­15

5

35.03

35.67

36.32

-10

14

26.65

27.06

27.48

-5

23

20.46

20.72

20.98

0

32

15.84

16.00

16.1

5

41

12.30

1.46

12.61

10

50

9.66

9.771

9.91

15

59

7.589

7.22

7.856

20

68

6.025

6.144

6.265

25

78

4.86

0.922

5.030

30

86

3.874

3.68

4.064

#7

Step Action
Temp Sensor Circuits:

No. Go to Step 8.

Decision
Yes. Replace rear HVAC
temperature sensor.

a. Disconnect rear HVAC temperature sensor connector (5213).
b. Measure resistance in circuit H77TSA (pin-13 connector 5210 to pin-1 connector 5213).
c. Measure resistance in circuit H77TSB (pin-12 connector 5210 to pin-2 connector 5213).
Do both circuits have continuity?
#8

No. Repair circuits as needed.

REPAIR STEP(s)

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IK1900230 ­ Rear A/C Blows Warm Air

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Not applicable
REMOVAL PROCEDURE:
Not Applicable
INSTALLATION PROCEDURE:
Not Applicable

WARRANTY INFORMATION
Warranty Claim Coding:
Group: 19030 ­ Auxiliary No­Idle HVAC
Noun: 638 - Electric HVAC Module
Standard Repair Time(s):

Step Description

Chassis

EngineSRT Hours

1

Blend Door Operation

ProStar/LoneStar

All

T­
0.3
Time

2

Blend Door Actuator

ProStar/LoneStar

All

T­
0.1
Time

3

Blend Door Signal

ProStar/LoneStar

All

T­
0.1
Time

4

Blend Door Operation

ProStar/LoneStar

All

T­
0.4
Time

5

Rear HVAC Discharge Temp
ProStar/LoneStar
Setting

All

T­
0.1
Time

6

Rear HVAC Temp Sensor
Voltage

ProStar/LoneStar

All

T­
0.1
Time

7

Temp Sensor Resistance

ProStar/LoneStar

All

T­
0.2
Time

8

Temp Sensor Circuits

ProStar/LoneStar

All

T­
0.1
Time

OTHER RESOURCES
Master Service Information Site

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