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Old 04-28-2011, 06:18 PM
npresley npresley is offline
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Join Date: Apr 2011
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Default No Power to A/C Compressor

I have a 98 B2500 2wd, reg cab, and reg bed. After 2 yrs & baby on the way, I've decided to get the A/C going again. The lines are a couple of years old, and I replaced the 2 inline pressure switches. The fuse has power across it and the switches are getting power. The relay is good, but I am only seeing .03 volts at the compressor. I have disconnected the low pressure switch and jumper its (harness) connector pins together (paper clip works). I then jumped the other (hi pressure switch), then both switches. The voltage was still .03V to the compressor. I do need to refill the system, but I can't get power to the compressor to cycle to fill it. What am I missing?
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Old 08-02-2011, 12:22 PM
sheltonfilms sheltonfilms is offline
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Join Date: Sep 2010
Posts: 1,633
Default Re: No Power to A/C Compressor

Cookeville huh. You ever head out to Knoxville any?

If this is anything like my 2000 2.5 the cycling and cutoff switches just ground a wire that goes to the PCM. So I don't know why you are getting power there.

The PCM is the big decision maker for the compressor. There is a purple wire that comes from your control switch that tells the PCM that the compressor should run in certain modes (A/C defrost etc). It sends 12V to the PCM.

The Black/Yellow wire goes from the switches to the PCM and show ground when both are switched on.

There are two wires that come from the PCM to the coil part of your WOT relay. One supplys voltage and the other grounds.

Power to the Relay comes straight from a fuse. Should be the "A/C clutch system" one.

This relay is a Single POle Double Throw. Which means when the relay is off your compressor should be on. But when the relay is activated the switch for the compressor is opened.

THe Grey/White wire goes from the relay to the compressor clutch.
Automotive Electronics Engineer
2000 XLT 2.5L A/T
Explorer OHC
Explorer Autodim Mirrors w/ Autolamps
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Old 06-21-2016, 11:17 AM
pfsecosky pfsecosky is offline
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Smile Re: No Power to A/C Compressor

My problem was that the ac would start after a while running the truck- 10 to 15 minutes. Tried the ac cycling pressure switch-ok. 12volts going to the ac solenoid relay but no voltage to the solenoid. Pulled out the ac solenoid relay and it was oxidized in the socket. Pulled it out, cleaned contacts and reinstalled. Now my ac is working just fine.
2002 4WD 3.0L V6
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Old 06-21-2016, 11:53 AM
ranger024x4 ranger024x4 is offline
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Join Date: Sep 2010
Posts: 5,278
Default Re: No Power to A/C Compressor

glad you got it fixed. hopefully it didnt take you 5 years to figure it out lol

2012 Buick Regal GS- 6mt
2014 Nissan Juke Nismo- the wifes daily
1989 300zx twin turbo- has a few things done
1995 Bronco Eddie Bauer.. 351 4x4.. project
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