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John, Master A.S.E Automotive technician
Category: Chevy
Satisfied Customers: 9176
Experience:  A.S.E MasterTechnician A1-A8 w/L1,38 years experience General Motors Master Technician
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2000 Chevrolet: Silverado..air conditioner compressor will not cycle.

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I have a 2000 Chevrolet 1500 Silverado pick up. The air conditioner compressor will not cycle. The compressor will come on even with the a/c button off. You can run it down the road for about 10 miles and it will be cold and then the a/c will go off and then you will have to wait about another 10 miles and it will come back on. I've replaced the a/c control, I've replaced the a/c relay, I've replaced the cycle switch and the low presure switch on the accumulator. None of this has changed the way it operates. It seems to have a mind of it's own. The gauge readings are good and the scan tool agrees that the gauge readings are good. The scan tool does read that the compressor is off, however, it is actually on. I don't know why it does this. I'm 51 and have been a mechanic since I was about 16. I can usually fix anything but this has me stumped. I would just like to get my a/c working in this hot Texas summer because I use this pick up to drive back and forth from work everyday. The pick up has 226,000 miles on it.
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john :

Hello & Welcome to JA,

john :

There is a possibility that the circuit from the computer is intermittenly shorted to ground somewhere the computer & the ac relay.
It is also possible that there could be a faulty circuit control driver in the computer,grounding the circuit when it should not.I would try to eliminate the circuit first & then try a computer.I am going to send some schematics to help you.
Be right back.

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Object Number: 606200  Size: FS

Customer: replied 7 years ago.
Would you be able to resend the 2nd schematic you sent? I couldn't print it out. I printed out the first one. Thank you>
Customer: replied 7 years ago.
Hi John, My husband has to be away from the computer for a few minutes. When he gets back, he may have another question for you. Thank you so much for your help so far. I think this is really going to help him.
You are very welcome.i have to go get a hot water heater ,so I may be away a little bit also,but we will get back together.
Customer: replied 7 years ago.
Sounds good!

Ok,see you in a bit.


Customer: replied 7 years ago.
Do you think that a shorted out Compressor Clutch Diode could cause the compressor not to cycle? Is the Diode located down by the compressor?
Only is the circuit is open.The diode is only there to keep voltage spikes from going back to the electrical system.I t used to be in the line near thew compressor,some have changes to the under hood electrical center.
Customer: replied 7 years ago.

Thanks for the information John. I'll be looking for that Diode. I guess the reason why I think that it might be the Diode is because the scan tool disagrees with the control. When the control says the compressor is off, the compressor is really on. I wonder if it could be feeding back through that Diode if current goes both directions.


Would we be able to finish discussing my truck on Monday. I need to BBQ for some friends coming over for the 4th. I've never used JustAnswer before so if I need to pay you now I can, or can we wait until after the 4th. Thank you so much for your help. This has been such a frustrating pick up problem.



No problem. You have a good 4th of July & I will talk to you Monday.
Customer: replied 7 years ago.



I have found that if I push on the compressor clutch while the engine is running and the a/c on, the clutch will re-engage and the a/c will cool until it cycles again. I think it has a bad clutch or the air gap is too wide. Do you concur with this?

Yes, you are exactly on target.
John and other Chevy Specialists are ready to help you
Customer: replied 7 years ago.

Thank you very much, John. You have been very helpful.



You are very welcome,Please have a good evening.