Q45 A/C Problem ?

[SteveA83]

I have a 97 Q45 and my a/c compressor will not turn on. I checked the relay. I have constant power , ignition power, but no ground from the computer to kick the relay over. I can power up the compressor from the yellow wire at the relay. I have good pressure on both the high and low sides. Also, using a scanner I was able to go into the inputs outputs of the ecm and saw that the ecm was being requested to turn on the a/c compressor and also to turn on the relay, but I still had no ground at the relay on the gr/b wire. I wondering if any of you have had this problem. I'm leaning towards the pressure switch on the reciever/dryer but not positive. Please Help ASAP

[DAEDALUS]

How about disconnect the switch(es) at their connectors and check for continuity?

[SteveA83]

its a four pin pressure switch what terminals would I check for continuity

[DAEDALUS]

If you look at the connector with the clip facing upward, here are the pins:

-- 2 14 3

There should be continuity between 1 and 4 (low and high pressure side).If there's no continuity then either the switch is bad or the pressure is either too high or too low.