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Home >> Jeep Truck >> 2009 >> Commander 4WD V8-4.7L >> Repair and Diagnosis >> Heating and Air Conditioning >> Testing and Inspection >> Symptom Related Diagnostic Procedures >> Rear A/C Heater Blend Door Inoperable

Rear A/C Heater Blend Door Inoperable






REAR A/C HEATER BLEND DOOR INOPERABLE





For a complete wiring diagram refer to the Wiring Information Electrical Diagrams.






1. VERIFY SYMPTOM
1. Turn the ignition on.
2. Set the rear blower on high.
3. Note temperature of the air exiting the Rear A/C Heater system vents.
4. Operate the Rear Blend Door Control.

Did the air change temperature (hot, mid-level, and cold)?

Yes

- The rear blend door actuator is working properly. Check for an intermittent condition by inspecting the related wiring harness for chafed, pierced, pinched, and partially broken wires. Also, inspect the related connectors for broken, bent, pushed out, spread, corroded, or contaminated terminals. Repair as necessary.

No

- Go To 2

2. CHECK JB FUSE #5 (F850) FUSED RUN RELAY OUTPUT CIRCUIT




1. Turn the rear blower off.
2. Using a 12-volt test light connected to ground, check for power on both sides of JB Fuse #5.

Does the test light illuminate brightly on both sides of the fuse?

Yes

- Go To 3

No - Open Fuse

- Using the Wiring Diagram as a guide, repair the (F850) Fused Run Relay Output circuit for a short to ground. Replace the fuse.
- Perform BODY VERIFICATION TEST Body Verification Test.

No - No Power to Fuse

- Using the Wiring Diagram as a guide, repair the (F850) Fused Run Relay Output circuit for an open.
- Perform BODY VERIFICATION TEST Body Verification Test.

3. CHECK THE (F850) FUSED RUN RELAY OUTPUT CIRCUIT FOR AN OPEN AT THE REAR A/C HEATER CONTROL




1. Measure the voltage of the (F850) Fused Run Relay Output circuit at the Rear A/C Heater Control C1 harness connector.

Is the voltage above 10 volts?

Yes

- Go To 4

No

- Repair the (F850) Fused Run Relay output circuit for an open.
- Perform BODY VERIFICATION TEST Body Verification Test.

4. CHECK THE (Z908) GROUND CIRCUIT FOR AN OPEN AT THE REAR A/C HEATER CONTROL




1. Turn the ignition off.
2. Disconnect the Rear A/C Heater Control C1 harness connector.
3. Measure the resistance between ground and the (Z908) Ground circuit at the A/C Heater Control C1 harness connector.

Is the resistance below 5.0 ohms?

Yes

- Go To 5

No

- Repair the (Z908) Ground circuit for an open.
- Perform BODY VERIFICATION TEST Body Verification Test.

5. CHECK THE (F850) FUSED RUN RELAY OUTPUT CIRCUIT FOR AN OPEN AT THE REAR BLEND DOOR ACTUATOR




1. Turn the ignition on.
2. Measure the voltage of the (F850) Fused Run Relay Output circuit at the Rear Blend Door Actuator harness connector.

Is the voltage above 10 volts?

Yes

- Go To 6

No

- Repair the (F850) Fused Run Relay output circuit for an open.
- Perform BODY VERIFICATION TEST Body Verification Test.

6. CHECK THE (Z908) GROUND CIRCUIT FOR AN OPEN AT THE REAR BLEND DOOR ACTUATOR




1. Turn the ignition off.
2. Disconnect the Rear Blend Door Actuator harness connector.
3. Measure the resistance between ground and the (Z908) Ground circuit at the Rear Blend Door Actuator harness connector.

Is the resistance below 5.0 ohms?

Yes

- Go To 7

No

- Repair the (Z908) Ground circuit for an open.
- Perform BODY VERIFICATION TEST Body Verification Test.

7. CHECK THE (C54) REAR BLEND DOOR CONTROL CIRCUIT FUNCTION




1. Reconnect the Rear A/C Heater Control C1 harness connector.
2. Turn the ignition on.
3. Measure the voltage of the (C54) Rear Blend Door Control circuit at the Rear Blend Door Actuator harness connector while moving the Blend Door Control on the Rear A/C Heater Control from Hot to Mid-Level to Cold.
4. The approximate Blend Door Control (C54) circuit voltage should be as follows:
5.
- Below 0.5 Volts @ Hot
- 2.0 Volts ± 0.5 Volts @ Mid-Level
- Within 0.5 Volts of Battery Voltage @ Cold

Is the voltage within specifications?

Yes

- Remove the Blend Door actuator from the A/C Heater Housing Assembly. By hand, attempt to rotate the actuator in both directions. Inspect the A/C Heater Housing for damage, and for a broken or binding door. Repair as necessary.
- Perform BODY VERIFICATION TEST Body Verification Test.

No - Voltage Remains Above 10 Volts

- Go To 8

No - Voltage Remains Below 2 Volts

- Go To 9

8. CHECK THE (C54) REAR BLEND DOOR CONTROL CIRCUIT FOR A SHORT TO THE (F850) FUSED RUN RELAY OUTPUT CIRCUIT AT THE REAR BLEND DOOR ACTUATOR




1. Turn ignition off.
2. Disconnect the Rear A/C Heater Control C1 harness connector.
3. Measure the resistance between the (C54) Rear Blend Door Control circuit and the (F850) Fused Run Relay Output circuit at the Rear Blend Door Actuator harness connector.

Is the resistance below 10k ohms?

Yes

- Repair the (C54) Rear Blend Door Control circuit for a short to the (F850) Fused Run Relay Output circuit.
- Perform BODY VERIFICATION TEST Body Verification Test.

No

- Replace the Rear A/C Heater Control.
- Perform BODY VERIFICATION TEST Body Verification Test.

9. CHECK THE (C54) REAR BLEND DOOR CONTROL CIRCUIT FOR A SHORT TO THE (Z908) GROUND CIRCUIT AT THE REAR BLEND DOOR ACTUATOR




1. Measure the resistance between the (C54) Rear Blend Door Control circuit and the (Z908) Ground circuit at the Rear Blend Door Actuator harness connector.

Is the resistance below 10k ohms?

Yes

- Repair the (C54) Rear Blend Door Control circuit for a short to the (Z908) Ground circuit.
- Perform BODY VERIFICATION TEST Body Verification Test.

No

- Go To 10

10. CHECK THE (C54) REAR BLEND DOOR CONTROL CIRCUIT FOR AN OPEN BETWEEN THE REAR BLEND DOOR ACTUATOR HARNESS CONNECTOR AND THE REAR A/C HEATER CONTROL HARNESS CONNECTOR




1. Measure the resistance of the (C54) Rear Blend Door Control circuit between the Rear Blend Door Actuator harness connector and the A/C Heater Control C1 harness connector.

Is the resistance below 5.0 ohms?

Yes

- Replace the Rear A/C Heater Control.
- Perform BODY VERIFICATION TEST Body Verification Test.

No

- Repair the (C54) Rear Blend Door Control circuit for an open.
- Perform BODY VERIFICATION TEST Body Verification Test.

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