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Rear Blower Motor Inoperative

REAR BLOWER MOTOR INOPERATIVE

Rear Blower Motor Inoperative:




POSSIBLE CAUSES
- PDC fuse #7 open
- JB fuse #10 open
- (C51) rear blower motor relay output circuit shorted to (Z911) ground
- (A611) fused B(+) circuit shorted to (Z911) ground circuit
- (C51) rear blower motor relay output circuit open or shorted to ground
- (A611) fused B(+) circuit open or shorted to ground
- (F921) fused run relay output open or shorted to ground
- (C105) rear A/C heater control circuit open or shorted to ground
- (C951) rear blower high speed circuit open
- (Z911) ground circuit open
- (C153) rear blower motor high speed circuit open
- (Z908) ground circuit open
- Junction block (JB)
- Power distribution center (PDC)
- Rear blower motor resistor
- Rear blower motor relay
- Rear blower motor
- Rear A/C heater control
- Upper switch bank

Diagnostic Test




1. CHECK PDC FUSE #7

Turn the ignition off.
Remove and inspect PDC Fuse #7.

Q: Is the fuse open?

YES: Replace the fuse and Go To 2.
NO: Reinstall the fuse and Go To 6.

2. CHECK REAR BLOWER MOTOR OPERATION

Turn the ignition on.
Turn the rear A/C heater control switch on in the upper switch bank.
Turn the rear blower on and operate it in all speeds.

Q: Does the rear blower motor operate properly without blowing the fuse?

YES: Check the (C51) Rear Blower Motor Relay Output circuit and the (A611) Fused B(+) circuit for a condition causing an intermittent short to ground. Repair as necessary. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 3




3. CHECK THE (C51) REAR BLOWER MOTOR RELAY OUTPUT CIRCUIT & THE (A611) FUSED B(+) CIRCUIT FOR A SHORT TO THE (Z911) GROUND CIRCUIT

Turn the ignition off.
Disconnect the Rear Blower Motor harness connector.
Remove the Rear Blower Motor Relay from the JB.
Measure the resistance between the (C51) Rear Blower Motor Relay Output circuit and the (Z911) Ground circuit in the Rear Blower Motor Relay connector.
Measure the resistance between the (A611) Fused B(+) circuit and the (Z911) Ground circuit in the Rear Blower Motor Relay connector.

Q: Is the resistance below 10K ohms on either circuit?

YES: Repair all circuits with a resistance below 10k ohms for a short to the (Z911) Ground circuit. Replace PDC Fuse #7. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 4




4. CHECK THE (C51) REAR BLOWER MOTOR RELAY OUTPUT CIRCUIT & THE (A611) FUSED B(+) CIRCUIT FOR A SHORT TO GROUND

Measure the resistance of the (C51) Rear Blower Motor Relay Output circuit between ground and the Rear Blower Motor Relay connector.
Measure the resistance of the (A611) Fused B(+) circuit between ground and the Rear Blower Motor Relay connector.

Q: Is the resistance below 10K ohms on either circuit?

YES: Repair all circuits with a resistance below 10k ohms for a short to ground. Replace PDC Fuse #7. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 5




5. CHECK REAR BLOWER MOTOR OPERATION WITH A SUBSTITUTE RELAY INSTALLED

Reconnect the Rear Blower Motor harness connector.
Install a substitute relay in place of the existing Rear Blower Motor Relay.
Turn the ignition on.
Turn the rear blower on and operate it in all speeds.

Q: Does the rear blower motor operate properly without blowing the fuse?

YES: Replace the original Rear Blower Motor Relay. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Replace the Rear Blower Motor. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test




6. CHECK JB FUSE #10

Remove and inspect JB Fuse #10.

Q: Is the fuse open?

YES: Go To 7
NO: Reinstall the fuse and Go To 10




7. CHECK THE (F921) FUSED RUN RELAY OUTPUT CIRCUIT FOR A SHORT TO GROUND

Disconnect the Upper Switch Bank harness connector.
Measure the resistance between ground and the (F921) Fused Run Relay Output circuit in the Upper Switch Bank harness connector.

Q: Is the resistance below 10k ohms?

YES: Repair the (F921) Fused Run Relay Output circuit for a short to ground. Replace JB fuse #10. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 8




8. CHECK THE (C105) REAR A/C HEATER CONTROL CIRCUIT FOR A SHORT TO GROUND

Remove the Rear Blower Motor Relay.
Measure the resistance between ground and the (C105) Rear A/C Heater Control circuit in the Upper Switch Bank harness connector

Q: Is the resistance below 10k ohms?

YES: Repair the (C105) circuit for a short to ground. Replace JB fuse #10. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 9




9. CHECK REAR BLOWER MOTOR OPERATION WITH A SUBSTITUTE RELAY INSTALLED

Replace JB fuse #10.
Connect the Upper Switch Bank harness connector.
Install a substitute relay in place of the existing Rear Blower Motor Relay.
Turn the ignition on.
Turn the rear A/C heater control switch on in the Upper Switch Bank.
Turn the rear blower on and operate it in all speeds.

Q: Does the rear blower motor operate properly without blowing the fuse?

YES: Replace the original Rear Blower Motor Relay. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Replace the Upper Switch Bank. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test




10. CHECK REAR BLOWER MOTOR OPERATION WITH A SUBSTITUTE RELAY INSTALLED

Install a substitute relay in place of the existing Rear Blower Motor Relay.
Turn the ignition on.
Turn the rear A/C heater control switch on in the upper switch bank.
Turn the rear blower on and operate it in all speeds.

Q: Does the rear blower motor operate properly?

YES: Replace the original Rear Blower Motor Relay. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 11




11. CHECK THE (Z911) GROUND CIRCUIT FOR AN OPEN

Turn the ignition off.
Turn the rear blower motor off.
Remove the substitute Rear Blower Motor Relay.

NOTE: The test light must illuminate brightly. Compare the brightness to that of a direct connection to the battery.

Using a 12-volt test light connected to 12 volts, probe the (Z911) Ground circuit in the Rear Blower Motor Relay connector.

Q: Does the test light illuminate brightly?

YES: Go To 12
NO: Repair the (Z911) Ground circuit for an open. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test




12. CHECK THE (C105) REAR A/C HEATER CONTROL CIRCUIT FOR VOLTAGE

Turn the ignition on.

NOTE: The test light must illuminate brightly. Compare the brightness to that of a direct connection to the battery.

Using a 12-volt test light connected to ground, probe the (C105) rear A/C heater control circuit in the Rear Blower Motor Relay connector.

Q: Does the test light illuminate brightly?

YES: Go To 16
NO: Go To 13




13. CHECK (F921) FUSED RUN RELAY OUTPUT CIRCUIT FOR AN OPEN

NOTE: The test light must illuminate brightly. Compare the brightness to that of a direct connection to the battery.

Using a 12-volt test light connected to ground, back probe the (F921) Fused Run Relay Output circuit in the Upper Switch Bank harness connector.

Q: Does the test light illuminate brightly?

YES: Go To 14
NO: Repair the (F921) Fused Run Relay Output circuit for an open. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test




14. CHECK THE (C105) REAR A/C HEATER CONTROL CIRCUIT FOR AN OPEN

Turn the ignition off.
Disconnect the Upper Switch Bank harness connector.
Measure the resistance of the (C105) Rear A/C Heater Control circuit between the Rear Blower Motor Relay connector and the Upper Switch Bank harness connector.

Q: Is the resistance below 5.0 ohms?

YES: Go To 15
NO: Repair the (C105) Rear A/C Heater Control circuit for an open. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test




15. CHECK THE UPPER SWITCH BANK

Install the original rear blower motor relay.
Connect a fused jumper wire between the (C105) Rear A/C Heater Control circuit and the (F921) Fuse Run Relay Output in the Upper Switch Bank harness connector.
Turn the ignition on.
Turn the rear blower on and operate it in all speeds.

Q: Does the rear blower motor operate properly?

YES: Replace the Upper Switch Bank. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 16




16. CHECK (A611) FUSED B(+) CIRCUIT FOR AN OPEN

Turn the rear blower motor off.
Turn the ignition off.
Remove the Rear Blower Motor Relay.
Remove the jumper wire from the Upper Switch Block harness connector.
Turn the ignition on.

NOTE: The test light must illuminate brightly. Compare the brightness to that of a direct connection to the battery.

Using a 12-volt test light connected to ground, probe the (A611) Fused B(+) circuit in the Rear Blower Motor Relay connector.

Q: Does the test light illuminate brightly?

YES: Go To 17
NO: Repair the (A611) Fused B(+) circuit for an open. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test




17. CHECK (C51) REAR BLOWER MOTOR RELAY OUTPUT CIRCUIT FOR AN OPEN

Turn the ignition off.
Install the Rear Blower Motor Relay.
Connect the Upper Switch Block harness connector.
Disconnect the Rear Blower Motor harness connector.
Turn the ignition on.

NOTE: The test light must illuminate brightly. Compare the brightness to that of a direct connection to the battery.

Using a 12-volt test light connected to ground, back probe the (C51) Blower Motor Relay Output circuit in the Rear Blower Motor harness connector.

Q: Does the test light illuminate brightly?

YES: Go To 18
NO: Repair the (C51) Blower Motor Relay Output circuit for an open. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test




18. CHECK REAR BLOWER MOTOR OPERATION BY BYPASSING THE A/C HEATER CONTROL

Turn the ignition off.
Reconnect the Rear Blower Motor harness connector.
Connect a jumper wire between ground and the (C951) Rear Blower High Speed circuit in the Rear Blower Motor harness connector.
Turn the ignition on.
Turn the rear A/C heater control switch on in the upper switch bank.

Q: Does the rear blower motor run at high speed?

YES: Go To 19
NO: Replace the Rear Blower Motor. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test




19. CHECK THE (C951) REAR BLOWER HIGH SPEED CIRCUIT, THE (C153) REAR BLOWER HIGH SPEED CIRCUIT, AND THE REAR BLOWER MOTOR RESISTOR BLOCK FOR AN OPEN

Turn the ignition off.
Remove the jumper wire from the Rear Blower Motor harness connector.
Disconnect the Rear A/C Heater Control C2 harness connector.
Disconnect the Rear Blower Motor harness connector.
Measure the resistance of the (C951) Rear Blower High Speed circuit and the (C153) Rear Blower High Speed circuit between the Rear A/C Heater Control C2 harness connector and the Rear Blower Motor harness connector.

Q: Is the resistance below 5.0 ohms?

YES: Go To 22
NO: Go To 20




20. CHECK THE (C153) REAR BLOWER HIGH SPEED CIRCUIT FOR AN OPEN

Disconnect the Rear Blower Motor Resistor Block harness connector.
Measure the resistance of the (C153) Rear Blower High Speed circuit between the Rear Blower Motor Resistor Block harness connector and the Rear A/C Heater Control C2 harness connector.

Q: Is the resistance below 5.0 ohms?

YES: Go To 21
NO: Repair the (C153) Rear Blower High Speed circuit for an open. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test




21. CHECK THE (C951) REAR BLOWER HIGH SPEED CIRCUIT FOR AN OPEN

Measure the resistance of the (C951) Rear Blower Motor High Speed circuit between the Rear Blower Motor Resistor harness connector and the Rear Blower Motor harness connector.

Q: Is the resistance below 5.0 ohms?

YES: Replace the Rear Blower Motor Resistor Block. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Repair the (C951) Rear Blower Motor High Speed circuit for an open. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test




22. CHECK THE (Z908) GROUND CIRCUIT FOR AN OPEN

Measure the resistance of the (Z908) Ground circuit between ground and the Rear A/C Heater Control C2 harness connector.

Q: Is the resistance below 5.0 ohms?

YES: Replace the Rear A/C Heater Control.
NO: Repair the (Z908) Ground circuit for an open. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
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