Hi. Really discouraged. I just bought a 2000 tahoe limited 5.7. The button on the dash will NOT enguage the compressor even though it lights up. My mechanic jumped the compressor clutch and it spun. A/C blew cold air. It is NOT the really, NOT the low-pres cutoff switch and NOT any fuses. Both myself and my mechanic are at a huge loss as what is could be. The climate cnt pannel seems to be ok. Temp control will go to hot and heater works, fan speed works, defrost works, and recirc button is operational. Anything else that would disable the compressor from engauging? Thanks in advance the help is greatly appreciated.

 

Check the connections on both ends and the wire itself. Also check to see that the compressor has a good ground.

 

Check the connector at the compressor with a voltmeter. If you don't have voltage, it is the relay, if you do, it is the clutch. If the relay coil is operating, you don't have voltage across the contacts.

 

Find a real mechanic that can trace out the electrical diagram. Are you sure there is a proper charge in the system so it will come on?

 

Hi. I worked with a mechanic for two hours yesterday and had no luck finding anything. I dont think its charge on the system bc it would'nt work even if we bypassed (jumped) the low-press cutoff switch.

 

If the relay coil is operating (energized), the permissive for BOTH low charge, and high pressure are not the issue. Do not assume it cannot be the high pressure switch (or low charge either)because the compressor isn't running, switch can be bad. If the clutch relay coil has battery voltage to it the system when switched on has a permissive for the compressor to run. The relay contacts have a seperate fused source when closed contacts from the realy, close you have voltage to the clutch.

If the relay coil IS NOT engaged, I'd suggest you take it to a mechanic. I cannot recommend jumpering out any safety switch in the system to determine what it is.

 

Since the A/C works when the 12V is applied to the clutch, he could check the pressures and if OK, go ahead and bypass the hi and lo pressure switches to rule them out. Personally I suspect the relay contacts.

 

Just changed the relay. no dice. i've been told that the hi-pres switch will not affect the compressor turning on or not. is this true? and to test, can i just use a paperclip and jump it like the low-press side? Thanks again.

 

This is WHY i wouldn't suggest you jumper anything. YES IT IS A PERMISSIVE FOR THE COMPRESSOR TO RUN!

 

To be honest, im having trouble understanding. i'm not seeing what you are thinking the problem to be? i appologize for my ignorance but what does the relay not being the problem prove? thanks and sorry for the ignorance.