air cond. wiring trouble - Chevelle Tech
Electrical & Wiring Troubleshooting electrical problems.

 
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post #1 of 13 (permalink) Old Aug 7th, 00, 12:20 AM Thread Starter
 
Join Date: Apr 1999
Location: california
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can anyone explain why this happens;

when i plug in the two prong wiring jack into the a/c compressor the a/c compressor clutch engages (clicks). the car is off and the engine is not running and the a/c switch is in the off position? I have not been able to find any crossed or shorted out wiring. if i start the car and plug in the a/c compressor it will engage and not turn off. im stumped. any help pleeeeese.
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post #2 of 13 (permalink) Old Aug 7th, 00, 8:13 AM
cb
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The reason is very simple. One of the two wires are connected to the battery. Finding the cause may not be so simple. Test meter or at least a test light and start tracing the "hot" wire back until you find the problem. Tip: if your car is wired correctly, the AC circuit should never be hot when the ign. key is off.
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post #3 of 13 (permalink) Old Aug 7th, 00, 11:33 AM
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Phil
 
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CHP
If you've checked your wiring as CB suggested and wiring is unmolested chances are the Master A/c switch behind the control panel has fused itself together keeping the compressor circut energized. also there is a relay on the fender which can also stick.
But if the car is off and its still hot something aint wired right

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Philip Mullaly
72 TPI El Camino
If the opposite of Pro is Con,wouldn't the opposite of Progress be Congress
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post #4 of 13 (permalink) Old Aug 7th, 00, 12:15 PM
 
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The A/C power wire runs thru the same harness as the High Fan Relay. The red wire on the High Fan Relay is connected directly to the primary buss (battery). The green (usually) wire on the A/C low pressure switch is also the A/C power wire that activates the compressor. Sounds like these wires are coming together somewhere, either shorted together, on the wrong terminal, or thru a short in the High Fan Relay. This wiring harness, the relay, and the pressure switch are all located next to the firewall passenger side. The other wire on the A/C compressor plug is a ground. Originally grounded to a stand off on the intake manifold. This stand off is usually missing or broken off. I grounded mine to the A/C compressor mounting brace.
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post #5 of 13 (permalink) Old Aug 7th, 00, 1:48 PM Thread Starter
 
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thanx for the advice. but check this out. I was checking the master switch and found that one of the gray wires from the a/c switch had a splice in it. I traced the spliced wire to the engine compartment behind the master cylinder. It was all tied together in a ball and when I untied it, it stretched to just about ehere the a/c compressor is. I then pulled off the tape surrounding the wiring and found where the big green wire (to a/c)was cut. so being the curious person i am i put the spliced wire into the a/c compressor. now the a/c compressor will engage when the ign. is on and when the car is running. the only problem now is if i turn it from max-norm to the vent or heater the compr. is still engaged! what the heck is going on here. i am hoping to fix the problem myself if i can as labor here in town is about $55/hr for troubleshooting. thanx again for the help..
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post #6 of 13 (permalink) Old Aug 7th, 00, 11:26 PM
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Sounds like the a/c relay on the fender is stuck closed.Or the master switch behind the panel is stuck on.(not the fan switch) Verify the switch hooking up a test light to the output side make sure you loose power when deselecting a/c. Or Ohm across the switch with leads removed. If that works normally go to the a/c relay on the fender uplug it and remove it from the fender unbend the tabs holding the dome on.Once its opened youll be able to see if the contact points are welded together. If thats not it then you can reassemble it with no worrys

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Philip Mullaly
72 TPI El Camino
If the opposite of Pro is Con,wouldn't the opposite of Progress be Congress
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post #7 of 13 (permalink) Old Aug 9th, 00, 6:06 AM Thread Starter
 
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ok, im having trouble locating that relay on the fender. i can follow some wires down under where the hood hinges are and it goes back under the fender above the wheelwell. is that what you are talking about?
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post #8 of 13 (permalink) Old Aug 9th, 00, 7:20 PM
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Phil
 
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Sorry chp, my Olds is on the fender on the chevelles with the a/c compressor on the left side of the engine I believe the relay is mounted on the core support.not too sure as my 72 chevelle was really hacked when I got it. If someone else doesn't help out Ill look in the books when I get home

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Philip Mullaly
72 TPI El Camino
If the opposite of Pro is Con,wouldn't the opposite of Progress be Congress
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post #9 of 13 (permalink) Old Aug 10th, 00, 12:01 AM
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chp email me I've got some questions for you can fax a print on thurs if needed
Tried to email you but undeliverable

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Philip Mullaly
72 TPI El Camino
If the opposite of Pro is Con,wouldn't the opposite of Progress be Congress
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post #10 of 13 (permalink) Old Aug 10th, 00, 2:43 AM Thread Starter
 
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thanx that would be great. ill email you with my correct email address.
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post #11 of 13 (permalink) Old Aug 10th, 00, 9:56 AM
 
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I figured I'ld add my small problem to the mix. I think my switch in the control panel is bad. Had it out once and tryed to fix it but the ac still not kicking on. Does anyone have a idea where to get this switch its been a real bight trying to find one, or a way to jury rig the wiring to get the AC to click on just to check the system out. Keep Cool.

Thanks

craig
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post #12 of 13 (permalink) Old Aug 10th, 00, 11:13 AM
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Phil
 
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craigly hook a ohm meter across the switch and see if you get continuity when selecting a/c also which switch one on the side(on/off) or at rear of panel? What year car?

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Philip Mullaly
72 TPI El Camino
If the opposite of Pro is Con,wouldn't the opposite of Progress be Congress

[This message has been edited by pmullaly (edited 08-10-2000).]
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post #13 of 13 (permalink) Old Aug 10th, 00, 12:10 PM
 
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69 chevelle SS. The contacts were all resodered but the ohms check is sporactic sometimes it works and sometimes it doesn't. I think the contacts are so worn that it functions only part of the time. I had the part number out of the assembly manual but its found connected to the rear of the control panel. I think it had 4 plugs and its a push button switch that the slide depresses. Its always been problem and it just gets worse even after trying to fix it. I've tried to find a new one but so far no luck. Thanks for any help you can give.

craig
69 Chevelle SS
Dove White, Black Vinyl Top
Black Interior, Auto
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