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Old 08-20-2019, 04:26 PM   #1
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Dash A/C

Need some troubleshooting help. My dash ac is not working, I checked and my pressure is ok but compressor is not kicking in, I took it to the shop, they checked everything for leaks tried to crank it up and still nothing checked the volts going into the compressor and it was only 4 volts we disconnect it and gave the compressor 12 volts direct from the battery and voila compressor kicked on and started cooling. Can anyone tell me what is causing the 4 volts at compressor connection? Is it a computer problem?

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Old 08-20-2019, 05:27 PM   #2
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Most all systems have a bianary or trinary [spelling?] switch which will cut the compressor off in the case of a too high of a pressure or too low. Most of the systems I am used too it is on the drier but mine is in one of the lines near the evaporator in front. I am going thru a no dash A/C problem now and have it down to bad compressor clutch. I am getting 12 volt but clutch not engaging. Your problem, from what you stated is different and electrical. It is strange to get a reading of 4 volts. Are you sure it was not 4mV.

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Old 08-20-2019, 05:30 PM   #3
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Year, make and model might help us help you.
2004 Monaco La Palma 36DBD, W22, 8.1, 7.1 MPG
2000 LEXUS RX300 FWD 22MPG 4020 LBS

Don't know where I'm going, spose I'll get there anyway.
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Old 08-20-2019, 05:51 PM   #4
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It is a 2000 HR Endeavor I rebuilt all the system about 1-1/2 year ago an it work fine. At time of rebuild I replaced the dryer, evacuate the system, vacuum it and filled with the right amount of oil and freon. Yesterday the ac guy evacuated the system and checked for leaks again. But when the compressor would not kick on is when we checked it and according to him we were getting only 4v, that is when we feed 12 volts directly from the battery and the compressor kicked on. The wire that goes to the compressor is a single line and it goes into the harness that goes to the place where the computer is on the right rear access under a black plastic cover.
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Old 08-21-2019, 07:11 AM   #5
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I agree that the Trinary switch is good candidate. Check voltage at the Trinary if you have 12V at the "COMP" terminal then your losing voltage somewhere to the compressor. But if your voltage is low (11V or less) a the the Trinary switch that mans your voltage is low coming to the Trinary switch (then check voltage at dash AC switch). Note that your setup may not have the "Fan power" depending on where your AC Condenser fan is located.
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Old 08-22-2019, 08:49 PM   #6
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Thanks for all the replies, had nor had time to check it since I have been busy, but I will check it an update you. Cheers
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Old 08-23-2019, 09:22 PM   #7
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Either switch or resistive wires or connector.

Never operate the a.c. in manner described other than a touch test as the safety switches prevent failure.

4 volts indicates all switches likely okay but a resistive connection.

Unplug at compressorclutch and measure voltage on wire, likely will be 12 volts.

Locate the switches and with a.c. on should be 12 vac both sides.

Do not tug or wiggle before measurements as this may fix by bumping an intermittent connection.

The clutch pulls a bit of current so a dirty connection can cause this.
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Old 09-12-2019, 08:44 AM   #8
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Finally have time to look into this AC thing. Someone had a diagram of the ac system. I am trying to locate the trienary switch with no luck. Also it speaks of a relay that feeds directly into the compressor. Looking for all of that, sorry is taken so long to update but I have gotten myself into helping a couple of guys with their construction projects and got to finish with them before I can get back to playing with the rv

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