HVAC SYSTEM (AUTO A/C) (DIAGNOSTICS) > Diagnostics for A/C System Malfunction

BLOWER MOTOR TURNS AROUND EARLY

TROUBLE SYMPTOM:

• The blower rotates even though the blower switch is not turned on.

• The blower motor continues to rotate at high speed. (Not adjustable.)

WIRING DIAGRAM:

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1.CHECK BLOWER MOTOR CIRCUIT.

1) Turn the ignition switch to OFF.

2) Disconnect the power transistor connector.

3) Use a tester to measure the resistance between the power transistor connector and chassis ground.

Connector & terminal

(B57) No. 3 — Chassis ground:

Is there continuity?

Repair or replace the short circuit of the harness.

2.CHECK HARNESS.

1) Remove the auto A/C control module.

2) Use a tester to measure the resistance between the power transistor connector and chassis ground.

Connector & terminal

(B57) No. 2 — Chassis ground:

Is there continuity?

Repair or replace the short circuit of the harness.

3.CHECK POWER TRANSISTOR.

1) Connect the disconnected connectors.

2) Turn the ignition switch to ON.

3) Use a tester to measure the voltage between the power transistor connector and chassis ground.

Connector & terminal

(B57) No. 2 (+) — Chassis ground (−):

Is the voltage approx. 10 V when fan dial in 1st, and approx. 1 V when fan dial in 7th?

Replace the power transistor.

4.CHECK AUTO A/C CONTROL MODULE.

1) Turn the fan speed control dial OFF.

2) Disconnect the power transistor connector.

3) Use a tester to measure the resistance between the power transistor connector and chassis ground.

Connector & terminal

(B57) No. 2 — Chassis ground:

When the fan speed control dial is OFF and other than OFF, does the resistance change?

Replace the power transistor.

Replace the auto A/C control module.