[dm600]

The ac clutch wont engage on my 98 frontier. I have checked every wire and component that i can see on the schematic and everything seems to be ok with the exception of I am not getting a ground signal from the ecu or pcm as the book calls it. Should the compressor clutch engage if you have the pressure switch jumpered even if the system is not running at the correct pressrues? What determines when the ecu tells the clutch to engage? I can get the clutch to engage if I jumper across the relay like the book tells to do as one of the checks. After that it says to take it to a dealer to have the PCM and related circuits checked. I'm lost. Not that keen with electrical problems as it is. HELP!!

 

[Whiffle]

Seems to me like its an electrical issue somewhere and not related to the pressure switch (I think it should come on if you jumper that switch) or the pressure being low.

Could it be that the ECM isn't getting the signal to turn on the A/C? I think I would check whatever inputs to the ECM, like the switch on the dash.

Which book are you working out of ?

 

[dm600]

98 frontier ac clutch not engaging

Im working out of a Haynes manual. The book doesnt go into talking about signals that pertain to the ecm. Or at least not in the air conditioning section. It looks to me like the ecm is suppose to ground the pink wire that goes to the ac relay. The other two at the relay have power when the switch is on. (the yellow is hot all the time and the green with orange stripe is hot when the key switch is on. The grean with black striped wire is the one that should run power from the relay to the compressor clutch and the iacv-ficd valve which I think is a throttle step up motor.