A/C Compressor does not kick in

[Danish Farmer]

Hi gyes

I had my A/C system filled up to see if it worked. (Truck has been sitting fot 1,5 years before I bought it last summer. Don`t know how many years ago A/C worked the last time.)

He says no leaks, the switch works, and the relay is clicking, but still the compressor does not get any electric power to it to engage.
Can you give a clue where to troubleshoot first ?

Regards
The owner of a lonely Silverado in Denmark, whit not much knowledge arround it ;0)

 

[THEFERMANATOR]

Take a piece of wire and jumper the low pressure switch(the switch that screws onto the accumulator, silver canister mounted near the firewall). Turn the truck on and turn the A/C on and see if it comes on or not. GM ran the power from the relay to the low pressure switch, and then to the compressor in 95, so it is a confusing system to those that don't know it, and the low pressure switch is a COMMON failure item on them.

 

[Danish Farmer]

Thank you for the help. I talked to them again and they claim that they allready tryed to jump the switch, but still no alectricity was supplyed to the compressor. Any other clues of where to troubleshoot before making a bypass wire ;0)

//Regards

 

[THEFERMANATOR]

Thank you for the help. I talked to them again and they claim that they allready tryed to jump the switch, but still no alectricity was supplyed to the compressor. Any other clues of where to troubleshoot before making a bypass wire ;0)

//Regards

make sure they put the jumper in the switch connector and turned teh truck on and teh A/C or else it will not come on. And the low pressure switch is the one on the canister mounted on the firewall. It is a confusing system to people to understand with the way GM wired it.

 

[THEFERMANATOR]

Heres the wiring diagram for the compressor circuit for a 95 SUBURBAN. Click on it to make it bigger.

 

[millsroger]

Did they get 12 volts TO the Low pressure switch???? Jumper direct to the compressor clutch with truck off, if it clicks in then it is top side supply, if not it is bottom side ground.

 

[millsroger]

Here is a diagram that shows a slightly different layout

 

[THEFERMANATOR]

View attachment 34020Here is a diagram that shows a slightly different layout

This one says it is for a 94, 95 is a completely different animal as far as the wiring goes. When I rewired my 95 for the engine swap, I veridied that the 95 diagram was correct to what came out so I knew how to modify it for the DMAX swap.

 

[millsroger]

Both show the relay first then the pressure switches in series to the compressor clutch, just different wiring colors and the voltage source. He said the relay energized but jumping the low pressure switch did not do it, that leaves the hi pressure switch and the clutch. Was thinking that he might have lost the twelve volt source for the clutch if separate from the twelve volt source for the relay. A quick check of the colors on the relay will tell which diagram is right.