94 K2500 ac not working. Controls work, relay in dash has 12.37v switched going out. But when I check at the compressor all I have is 0.05v. Checked for a break where the diode is cliped into the line and it's only 0.05v there too. Is there another relay between the in dash (next to glove box) relay and the wire comeing out the firewall?
There is a low pressure switch at the evaporator, and a high pressure switch in the compressor - either will break the clutch circuit.
A second hp switch prevents the controller from functioning.
I would suspect the evaporator switch is open, indicating low freon.
And, this is certainly no admission to or of guruism!
Enthusiast
there is a pressure switch tapped into the evapoator(aluminum can just off firewall) that will not allow the compressor to kick on unless there is proper pressure in the system. if you jump the two wires together that go to that switch, start truck w/ac off, then turn ac on. if compressor clutch kicks on now- you have low pressure in the freon system check for leaks w/kit or have shop check it out. DO NOT leave the pressure switch bypassed it is designed to keep the compressor from pumping when there is not enough pressure and WILL lead to damage if bypassed. This is just a method of diagnosis not a fix. good luck
Enthusiast
not anything near a guru here either just somone who has always HAD to work through problems myself. also my father did ECS (environmental control systems) in the air force which pretty much is a/c and then went on to other refridgeration.
Thank you fellow allumni from SOHK.
Did put in a new condensor last year. Along with new seals. A leak is possible. Have to go out and try the jumper trick. And yes I understand no freon/no oil!
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