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 in all speeds? | -- | 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 |

1. Turn the ignition switch to the ON position.
2. Turn the blower switch to M3.
3. Use the J 39200 Digital Multimeter (DMM) in order to backprobe the blower resistor assembly.
4. Measure the voltage between terminal E and ground.

Does the voltage measured equal the specified value?

battery positive voltage

Go to Step 4

Go to Step 5

4 |

1. Use the J 39200 DMM in order to backprobe the underhood wiring harness junction block connector C3.
2. Measure the voltage between terminal C10 and ground.

Does the voltage measured equal the specified value?

battery positive voltage

Go to Step 6

Go to Step 7

5 | Replace the blower resistor assembly. Refer to Blower Motor Resistor Replacement in HVAC. Is the repair complete? | -- | Go to HVAC Blower Controls System Check in HVAC. | --
6 | Replace the underhood wiring harness junction block. Refer to Underhood Fuse Block Replacement . Is the repair complete? | -- | Go to HVAC Blower Controls System Check in HVAC. | --
7 | Repair the open in CKT 101 between the blower resistor assembly and the underhood wiring harness junction block. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to HVAC Blower Controls System Check in HVAC. | --