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MTC

BLOWER MOTOR INOPERATIVE (MTC)

Blower Motor Inoperative (MTC):





POSSIBLE CAUSES
- PDC fuse #1 open
- JB fuse #10 open
- (C7) blower motor relay output circuit shorted to (Z387) ground circuit
- (A502) fused B(+) circuit shorted to (Z387) ground circuit
- (C7) blower motor relay output circuit shorted to ground
- (A502) fused B(+) circuit shorted to ground
- (F921) fused run relay output circuit shorted to ground
- (C75) blower high speed circuit open
- (Z387) ground circuit open
- (F921) fused run relay output circuit open
- (A502) fused B(+) circuit open
- (C7) blower motor relay output circuit open
- (C41) blower switch position signal circuit shorted to (C121) sensor ground circuit
- (C41) blower switch position signal circuit shorted to ground
- (C41) blower switch position signal circuit open
- (Z134) ground circuit open
- Junction block (JB)
- Power distribution center (PDC)
- Blower motor relay
- Blower motor
- A/C heater control

Diagnostic Test




1. CHECK PDC FUSE #1

Turn the ignition off.
Remove and inspect PDC Fuse #1.

Q: Is the fuse open?

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

2. CHECK BLOWER MOTOR OPERATION

Turn the ignition on.
Turn the blower on and operate it in all speeds.

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

YES: Check the (C7) Blower Motor Relay Output circuit and the (A502) 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 (C7) BLOWER MOTOR RELAY OUTPUT CIRCUIT & THE (A502) FUSED B(+) CIRCUIT FOR A SHORT TO THE (Z387) GROUND CIRCUIT

Turn the ignition off.
Disconnect the Blower Motor harness connector. Remove the Blower Motor Relay from the PDC. Measure the resistance between the (C7) Blower Motor Relay Output circuit and the (Z387) Ground circuit in the Blower Motor Relay connector.
Measure the resistance between the (A502) Fused B(+) circuit and the (Z387) Ground circuit in the 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 (Z387) Ground circuit. Replace PDC Fuse #1. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 4




4. CHECK THE (C7) BLOWER MOTOR RELAY OUTPUT CIRCUIT & THE (A502) FUSED B(+) CIRCUIT FOR A SHORT TO GROUND

Measure the resistance of the (C7) Blower Motor Relay Output circuit between ground and the Blower Motor Relay connector.
Measure the resistance of the (A502) Fused B(+) circuit between ground and the 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 #1. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 5




5. CHECK BLOWER MOTOR OPERATION WITH A SUBSTITUTE RELAY INSTALLED

Reconnect the Blower Motor harness connector.
Replace PDC Fuse #1.
Install a substitute relay in place of the existing Blower Motor Relay.
Turn the ignition on.
Turn the blower on and operate it in all speeds.

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

YES: Replace the original Blower Motor Relay. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Replace the Blower Motor. Replace the fuse and original Blower Motor Relay. 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: Using the wiring schematics as a guide, check the (F921) Fused Run Relay Output circuit for a condition causing a short to ground. Repair as necessary. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Reinstall the fuse and Go To 7.




7. CHECK BLOWER MOTOR OPERATION WITH A SUBSTITUTE RELAY INSTALLED

Install a substitute relay in place of the existing Blower Motor Relay in the PDC.
Turn the ignition on.
Turn the blower on and operate it in all speeds.

Q: Does the blower motor operate properly?

YES: Replace the original Blower Motor Relay. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 8




8. CHECK THE (Z387) GROUND CIRCUIT FOR AN OPEN

Turn the ignition off.
Remove the substitute 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 (Z387) Ground circuit in the Blower Motor Relay connector.

Q: Does the test light illuminate brightly?

YES: Go To 9
NO: Repair the (Z387) Ground circuit for an open. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test




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

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 (F921) Fused Run Relay Output circuit in the Blower Motor Relay connector.

Q: Does the test light illuminate brightly?

YES: Go To 10
NO: Repair the (F921) Fused Run Relay Output circuit for an open. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test




10. CHECK (A502) FUSED B(+) 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, probe the (A502) Fused B(+) circuit in the Blower Motor Relay connector.

Q: Does the test light illuminate brightly?

YES: Go To 11
NO: Repair the (A502) Fused B(+) circuit for an open. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test




11. CHECK (C7) BLOWER MOTOR RELAY OUTPUT CIRCUIT FOR AN OPEN

Turn the ignition off.
Install the original Blower Motor Relay.
Disconnect the 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 (C7) Blower Motor Relay Output circuit in the Blower Motor harness connector.

Q: Does the test light illuminate brightly?

YES: Go To 12
NO: Repair the (C7) Blower Motor Relay Output circuit for an open. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test




12. CHECK THE (C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT FOR A SHORT TO THE (C121) SENSOR GROUND CIRCUIT

Turn the ignition off.
Disconnect the A/C Heater Control C2 harness connector.
Measure the resistance between the (C41) Blower Switch Position Signal circuit and the (C121) Sensor Ground circuit in the A/C Heater Control C2 harness connector.

Q: Is the resistance below 10K ohms?

YES: Repair the (C41) Blower Switch Position Signal circuit for a short to the (C121) Sensor Ground circuit. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 13




13. CHECK THE (C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT FOR A SHORT TO GROUND

Disconnect the A/C Heater Control C3 harness connector.
Measure the resistance of the (C41) Blower Switch Position Signal circuit between ground and the A/C Heater Control C3 harness connector.

Q: Is the resistance below 10K ohms?

YES: Repair the (C41) Blower Switch Position Signal circuit for a short to ground. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 14




14. CHECK (C41) BLOWER SWITCH POSITION SIGNAL CIRCUIT FOR AN OPEN

Measure the resistance of the (C41) Blower Switch Position Signal circuit between the A/C Heater Control C2 harness connector and the A/C Heater Control C3 harness connector.

Q: Is the resistance below 5.0 ohms?

YES: Go To 15
NO: Repair the (C41) Blower Switch Position Signal circuit for an open. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test




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

Reconnect the A/C Heater Control C2 harness connector.
Reconnect the A/C Heater Control C3 harness connector.
Reconnect the Blower Motor harness connector.
Connect a jumper wire between ground and the (C75) Blower High Speed circuit in the Blower Motor harness connector.
Turn the ignition on.

Q: Does the blower motor run at high speed?

YES: Go To 16
NO: Replace the Blower Motor. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test




16. CHECK THE (C75) BLOWER HIGH SPEED CIRCUIT FOR AN OPEN

Turn the ignition off.
Disconnect the A/C Heater Control C3 harness connector.
Disconnect the Blower Motor harness connector.
Measure the resistance of the (C75) Blower High Speed circuit between the A/C Heater Control C3 harness connector and the Blower Motor harness connector.

Q: Is the resistance below 5.0 ohms?

YES: Go To 17
NO: Repair the (C75) Blower High Speed circuit for an open. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test




17. CHECK THE (Z134) GROUND CIRCUIT FOR AN OPEN

Measure the resistance of the (Z134) Ground circuit between around and the A/C Heater Control C3 harness connector.

Q: Is the resistance below 5.0 ohms?

YES: Replace the A/C Heater Control.
NO: Repair the (Z134) Ground circuit for an open. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
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