I have a 2000 civic ex that i cant get the air conditioner compressor to engage. ive traced it down to no signal coming from the ecm to the clutch relay on the ground side.I have power to the relay but no ground.

 

Does the condenser fan run?

With the key in ON(II), do you measure battery voltage at ECU terminal A17? Is there continuity across the two terminals of the A/C pressure switch?

 

If the engine idle speed increases the ECU is getting the signal from the pressure switch, but not closing the relay so must be bad ECU (which is very rare). If not it is probably not getting the signal on the blue and red wire. That wire goes to ground through the pressure switch when the compressor should be on.

 

Yes the fan runs.There is continuityacross the terminals.Which terminal is a17 and how much voltage?I dont have a ground signal coming out of the ecu theblack red wire to the ac clutch relay.Ican jump across the hot terminals on the relay and get power to the ac clutch.