1. Disconnect the automatic temperature control (ATC) controller connectors A and B.
2. Disconnect the connectors from the power transistor.
3. Measure the resistance circuit GY/BK from terminal 4 of the power transistor to terminal B1 of the ATC controller.

Does the resistance measured equal the specified value?

0 ohms

Go to Step 2

Go to Step 6

Measure the resistance in the circuit from terminal 1 of the power transistor to terminal B12 of the ATC controller.

Does the resistance measured equal the specified value?

0 ohms

Go to Step 3

Go to Step 6

1. Connect the wiring harness to the ATC controller and to the power transistor.
2. Turn the ignition switch to ON.
3. Measure the voltage from ground to terminal B12 of the ATC controller.
4. Cycle the fan speed controller manually from the lowest speed (1) to the highest speed (8).

Do the voltages measured match approximately the specified values within ±0.5 V?

1: 4.0 V

2: 5.0 V

3: 6.0 V

4: 7.0 V

5: 8.0 V

6: 9.0 V

7: 10.0 V

8: Max HI

Go to Step 4

Go to Step 5

Replace the ATC controller.

Did you complete the replacement?

--

System OK

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Measure the resistance in circuit (Violet) between terminal 6 of the power transistor and the blower motor terminal 2.

Does the resistance measured equal the specified value?

0 ohms

Go to Step 7

Go to Step 6

Repair or replace the wiring harness for the circuit (Violet).

Did you complete the repair or replacement?

--

System OK

--

Inspect the wiring harness of the motor and power supply.

Is there any problem in the wiring, the relay, or the fuse?

--

Go to Step 9

Go to Step 8

Replace the power transistor.

Did you complete the replacement?

--

System OK

--

Repair or replace the wiring harness, the relay, or the fuse as required.

Did you complete the repair or replacement?

--

System OK

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