B1070

B1070-REAR BLOWER CONTROL CIRCUIT HIGH (ATC)

B1070-Rear Blower Control Circuit High (ATC):

WHEN MONITORED
When rear blower speed is set to Low, M1, or High with the ignition on.

SET CONDITION
If the ATC detects an excessive draw on any of the rear blower outputs.

POSSIBLE CAUSES
- High resistance on (z928) ground circuit
- (C151) rear blower low speed circuit, (C152) rear blower medium speed circuit, or (C153) rear blower high speed circuit shorted to voltage
- Blockage stalling rear blower motor
- Rear blower motor resistor block
- Rear blower motor
- A/C heater control

NOTE: This DTC must be active for the results of this test to be valid. Do not perform this test if this DTC is stored. Refer to HVAC System Test (ATC) for stored DTC test procedures. HVAC System Test (ATC)

Diagnostic Test

1. CHECK (Z928) GROUND CIRCUIT FOR HIGH RESISTANCE




Turn the ignition off.
Disconnect the A/C Heater Control C3 harness connector.
Measure the resistance of the (Z928) Ground circuit between ground and the A/C Heater Control C3 harness connector.

Q: Is resistance below 5.0 ohms?

YES: Go To 2
NO: Repair the (Z928) Ground circuit for high resistance. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

2. CHECK (C151) REAR BLOWER LOW SPEED CIRCUIT, (C152) REAR BLOWER MEDIUM SPEED CIRCUIT, & (153) REAR BLOWER HIGH SPEED CIRCUIT FOR SHORT TO VOLTAGE




Disconnect the Rear Blower Motor harness connector.
Turn the ignition on.
Measure the voltage of the (C151) Rear Blower Low Speed circuit in the A/C Heater Control C3 harness connector.
Measure the voltage of the (C152) Rear Blower Medium Speed circuit in the A/C Heater Control C3 harness connector.
Measure the voltage of the (C153) Rear Blower High Speed circuit in the A/C Heater Control C3 harness connector.

Q: Is voltage above 0.2 volts on any of the circuits?

YES: Repair the circuit(s) with voltage above 0.2 volts for a short to voltage. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 3

3. CHECK FOR BLOCKAGE PREVENTING REAR BLOWER MOTOR OPERATION
Turn the ignition off.
Remove the Rear Blower Motor from the Rear A/C Heater Housing in accordance with the Service Information.
Look for anything on the Rear Blower Motor and in the Rear A/C Heater Housing that is physically preventing rear blower operation.

Q: Is anything physically preventing rear blower operation?

YES: Repair as necessary. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Go To 4

4. CHECK REAR BLOWER MOTOR FOR CAUSE OF HIGH AMPERAGE DRAW




Reinstall the Rear Blower Motor in the Rear A/C Heater Housing in accordance with the Service Information.
Reconnect the Rear Blower Motor harness connector.
Disconnect the Rear Blower Motor Resistor Block harness connector.
Connect a 20 amp fused jumper wire between ground and the (C153) Rear Blower High Speed circuit in the Rear Blower Motor Harness connector.
Start the engine. The rear blower motor should run with out blowing the fuse.

Q: Does the rear blower motor run with out blowing the fuse?

YES: Go To 5
NO: Replace the Rear Blower Motor in accordance with the Service Information. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test

5. CHECK REAR BLOWER MOTOR RESISTOR BLOCK FOR CAUSE OF HIGH AMPERAGE DRAW




Turn the ignition off.
Remove the 20 amp fused jumper wire from the (C153) Rear Blower
High Speed circuit in the Rear Blower Motor Harness connector.
Reconnect the Rear Blower Motor Resistor Block harness connector.
Connect a 10 amp fused jumper wire between ground and the (C152) Rear Blower Medium Speed circuit in the Rear Blower Motor Resistor Block harness connector.
Start the engine. The rear blower motor should run with out blowing the fuse.
Turn the ignition off.
Remove the 10 amp fused jumper wire from the (C152) Rear Blower Medium Speed circuit in the Rear Blower Motor Resistor Block harness connector.
Connect a 5 amp fused jumper wire between ground and the (C151) Rear Blower Low Speed circuit in the Rear Blower Motor Resistor Block harness connector.
Start the engine. The rear blower motor should run with out blowing the fuse.

Q: Does the rear blower motor run with out blowing either of the fuses?

YES: Replace the A/C Heater Control in accordance with the Service Information. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test
NO: Replace the Rear Blower Motor Resistor Block in accordance with the Service Information. Perform BODY VERIFICATION TEST - VER 1. Body Verification Test