Cannot figure out why AC will not work. AC shows on on dash but compressor clutch does not engage and condenser fan does not come on. Blower works fine on all settings. Compressor, condenser, expansion, valve, drier, and AC pressure switch have all been replaced. System was vacuum and charged. Pressure is good. Can jump both the compressor clutch and condenser fan at the relay and both operate just fine. Any ideas?

 

The common DIY thread on top of the gen tech help forum has a HVAC diagnostic procedure you should try. That may help direct you what to test next.

 

Have tried diagnostic procedure. Shows no codes. Have also went through the AC pressure switch troubleshooting from the shop manual. Seems as if the Ecm is not grounding pin on relay to engage the compressor clutch.

 

See attached circuit diagram. I did not have an 07 manual.

If no ground signal is arriving from ECM/PCM then either faulty ECM/PCM, wiring fault on inputs, faulty Relay Module, faulty Gauge Control Module, or fault on Climate Control board.

Difficult problem to diagnose w/o sophisticated Honda HDS.

Check for Ground pass-through at the Relay Module. Absence of ground would inhibit AC system.

good luck

 

Thanks for the info. When you say the relay module, is that something other than the AC clutch relay? If so, do you know where that is located?

 

It's a different relay or component in the under hood fuse box. See diagram note *1.

The Relay Module's design/function is unclear. Some type of isolation device presumably.

good luck