For 1990-2009 cars

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you review the HVAC operation and perform the necessary inspections? | -- | Go to Step 2 | Go to Symptoms - HVAC Systems - Manual
2 | Exchange the blower motor relay with a known good relay from the underhood wiring harness junction block. Does the blower motor operate at high speed? | -- | Go to Step 3 | Go to Step 4
3 | Replace the faulty relay. Is the repair complete? | -- | System OK | --
4 |

1. Turn the ignition switch to the RUN position.
2. Turn the blower switch to HIGH.
3. Use the J 39200 Digital Multimeter (DMM) in order to backprobe the underhood wiring harness junction block connector C3.
4. Measure the voltage between terminal D9 and ground.

Does the voltage measured equal the specified value?

battery positive voltage

Go to Step 7

Go to Step 5

5 |

1. Use the J 39200 DMM in order to backprobe the heater A/C control assembly connector C1.
2. Measure the voltage between terminal C and ground.

Does the voltage measured equal the specified value?

battery positive voltage

Go to Step 8

Go to Step 6

6 | Replace the heater A/C control assembly. Refer to Control Assembly Replacement . Is the repair complete? | -- | System OK | --
7 | Using a test lamp, backprobe the underhood wiring harness junction block connector C3 between terminal D9 and terminal A10. Does the test lamp light? | -- | Go to Step 9 | Go to Step 10
8 | Repair the open in CKT 52 between the heater A/C control assembly and the underhood wiring harness junction block. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | System OK | --
9 | Replace the underhood wiring harness junction block. Refer to Underhood Fuse Block Replacement in Engine Electrical. Is the repair complete? | -- | System OK | --
10 | Repair the open in CKT 150 between the underhood wiring harness junction block and ground splice pack G201. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | System OK | --