HVAC Control Power And Ground Circuit Troubleshooting (Without Climate Control)

HVAC Control Power and Ground Circuit Troubleshooting

1. Check the No. 36 (10 A) fuse in the under-dash fuse/relay box.

Is the fuse OK?

YES -

Go to step 2.

NO -

Check for a short in the No. 36 (10 A) fuse circuit.�

2. Disconnect the HVAC control unit 28P connector.

3. Turn the ignition switch to ON (II).

4. Measure the voltage between the HVAC control unit 28P connector terminal No. 27 and body ground.





Is there battery voltage?

YES -

Go to step 5.

NO -

Repair an open in the wire between the No. 36 (10 A) fuse in the under-dash fuse/relay box and the HVAC control unit.�

5. Turn the ignition switch to LOCK (0).

6. Check for continuity between the HVAC control unit 28P connector terminal No. 18 and body ground.





Is there continuity?

YES -

Check for loose wires or poor connections at the HVAC control unit 28P connector. If the connections are good, substitute a known-good HVAC control unit, and recheck.�

NO -

Check for an open in the wire between the HVAC control unit and body ground. If the wire is OK, check for poor ground at G503.�