For 1990-2009 cars

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
Important: A short to ground will cause an open fuse(s). Before performing this diagnostic procedure, inspect the fuse(s) for an open.
1 | Exchange the blower motor relay with a known good relay from the underhood wiring harness junction block. Does the blower motor operate? | -- | Go to Step 2 | Go to Step 3
2 | Replace the faulty relay. Is the repair complete? | -- | Go to HVAC Blower Controls System Check in HVAC | --
3 | Backprobe the underhood wiring harness junction block connector C3 using a fused jumper between terminal B9 and B+. Does the blower motor operate? | -- | Go to Step 9 | Go to Step 4
4 |

1. Turn the ignition switch to the RUN position.
2. Turn the blower switch to M3.
3. Disconnect the blower motor connector.
4. Connect a test lamp between terminal B of the blower motor connector and ground.

Does the test lamp light?

--

Go to Step 5

Go to Step 6

5 | Connect a test lamp between terminal A and terminal B of the blower motor connector. Does the test lamp light? | -- | Go to Step 7 | Go to Step 8
6 | Repair the open in CKT 65 between the underhood wiring harness junction block and the blower motor. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to HVAC Blower Controls System Check in HVAC | --
7 | Replace the blower motor. Refer to Blower Motor and Fan Replacement . Is the repair complete? | -- | Go to HVAC Blower Controls System Check in HVAC | --
8 | Repair the open in CKT 250 between the blower motor and ground splice pack G203. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to HVAC Blower Controls System Check in HVAC | --
9 |

1. Turn the ignition switch to the RUN position.
2. Use the J 39200 Digital Multimeter (DMM) in order to backprobe the heater A/C control assembly connector C1.
3. Measure the voltage between terminal B and ground.

Does the voltage measured equal the specified value?

B+

Go to Step 13

Go to Step 10

10 |

1. Use the J 39200 DMM in order to backprobe the right side IP wiring harness junction block connector C1.
2. Measure the voltage between terminal A5 and ground.

Does the voltage measured equal the specified value?

B+

Go to Step 11

Go to Step 12

11 | Repair the open in CKT 641 between the right side IP wiring harness junction block and the heater A/C control assembly. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to HVAC Blower Controls System Check in HVAC | --
12 | Replace the right side IP wiring harness junction block. Is the repair complete? | -- | Go to HVAC Blower Controls System Check in HVAC | --
13 |

1. Turn the blower switch to M3.
2. Use the J 39200 DMM in order to backprobe the heater A/C control assembly connector C1.
3. Measure the voltage between terminal E and ground.

Does the voltage measured equal the specified value?

B+

Go to Step 14

Go to Step 15

14 | Replace the underhood wiring harness junction block. Refer to Underhood Fuse Block Replacement in Engine Electrical. Is the repair complete? | -- | Go to HVAC Blower Controls System Check in HVAC | --
15 | Replace the heater A/C control assembly. Refer to Control Assembly Replacement in HVAC. Is the repair complete? | -- | Go to HVAC Blower Controls System Check in HVAC | --