I've got an 07 Accord where the a/c is inop. Freon is full. It is manual HVAC. Going through some schematics I was able to obtain and I'm getting good pressure sensor signal to the control head and good temp sensor reading at the control head. The a/c indicator on the a/c button on the control head lights up, but ECM does not engage compressor. If I ground the a/c clutch relay control wire at ECM, compressor kicks in. Tried a control head and have same problem. Please help..........

 

Do both fans on the radiator turn on when you turn on the a/c with the engine running?

The wiring diagram I have shows the a/c pressure getting power from the relay module in the under hood fuse box.

The relay module is also connected to the gauge control module (can't tell if it is network connection or power). The gauge control module has a CAN lines (network communication) with the PCM. I am not sure how these units talk to each other.

Before condemning the PCM, try reading the HVAC codes. See the common DIY thread on top of the gen tech help forum. There is a post for HVAC codes.

You may want to try a gauge control module test as well.

Push and hold the trip/reset button.
Turn on headlights
turn ignition switch on (II position)
Within 5 seconds turn the headlights, OFF, then ON, then OFF.
Within 5 seconds, release the trip/reset button, and then push and release the button 3 times.

This should start the self diagnostic function. The gauge should do some bulb checks, then move the gauge needles to max, then return to min. Eventually, the cluster will show 888888 for normal or Error 1, 2 , or 3. That should be the end of the diagnostic.

Is there any chance you have a scan tool? It may make some of this testing easier.

 

I have a Genisys scanner, but do have access to a Snap-on scanner.

 

Both fans do come on when the a/c is turned on. I am getting 10,5 volts out of the relay module through the pressure sensor to the control head.

 

You can try your genisys scanner to read the CAN (network) for error codes. The snap-on may provide you more information.

Newer accords from 2003 to present are harder to diagnose, because the PCM controls a lot of functions, where older accords could be diagnosed with a volt meter or test light

 

Well,I have determined that the ECM is bad. Using snap-on scanner adn under ECM data the a/c clutch status is "on" and a/c button is "on" and changes when pushing the a/c button on the control head. Then when commanding a/c clutch on it would say "on" butm was not grounding the relay. So my question is can you use a used ECM or not, and if so does it have to be programmed by Honda?

 

A used PCM will work but you will have to program the keys. Before swapping the PCM, connect the snap-on scanner to see if can program keys. I also think you will have to do the idle relearn procedure, so check if the snap-on scanner has that function too.

 

Thank you very much!!