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post #1 of 10 (permalink) Old 09-29-2007, 03:39 PM Thread Starter
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Question AC woes....

Granted in Ohio I never had to worry about this kind of stuff since it never gets too hot but now that I'm in Houston, wow..... Black cat + No AC = death wish.

This is what's going on with my 92 LS with the 3.6L motor. When I turn the AC on the compressor tries to kick on, then kicks back off again in about 20 second intervals. I just had the system charged yesterday by an AC shop but they are closed on the weekend so I figure I would see if there is something I could fix to make everything work. When I left the shop it was blowing cold, got warm then got cold again, I could feel the compressor kick on that second time. When I took it on the highway the compressor shut off and now it is cycling on and off like I described above. I replaced the pressure switch on the accumulator but that didn't seem to do anything different.

Any suggestions or tests I could perform to check this? I bought another can of R134a with stop leak but the pressure gauge shows the system still has plenty of pressure in it. I jumped out the pressure switch which makes the compressor come on all the time but the air in the car is still warm even though the line going through the firewall gets 'frosty'. (This car had been switched to R134a, I know it came with R12 at first but the previous owner converted it).
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post #2 of 10 (permalink) Old 09-29-2007, 04:21 PM
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Did you check the pressure with the system on and the pressure switchjumped/bypassed? What was the pressure? Which climate control unit do you have? The short cycling is typical of an undercharged system but not typical of any other problem (the only other device that disables the compressor any other time would be the 'wot' compressor disable)

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post #3 of 10 (permalink) Old 09-29-2007, 04:59 PM Thread Starter
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I didn't check the pressure at both positions, I will give that a shot. I haven't added any 134a to the system since the 'idiot' gauge is in the red but I think it is only around 65psi and the guy that charged the system stuck 100psi in it I believe.
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post #4 of 10 (permalink) Old 09-29-2007, 08:03 PM Thread Starter
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Checking the pressure when jumping the switch it drops to 25 psi. When the compressor is off it goes up to 100psi.

Does that narrow the problem at all? What should system pressure be while running and while not?
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post #5 of 10 (permalink) Old 09-29-2007, 08:22 PM
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When I took my compressor off my 97' the clutch was rusted. Used Ford parts. Compressor, pulley, clutch. About $500. Accumulator will also be needed. Had to buy it from somewhere else. Replaced the condensor too. Should have replaced the AC muffler but did not have time. It was rusted but still doing it's primal job. The AC now works better than it has since I bought the car, which is so so. I think the car needs a bigger fan on the radiator and on the interior blower to get good results. Pay close attention to the compressor right now, because when it decides not to spin it will burn the serpentine belt right now. Burning rubber should come from the rear of the car, not from under the hood.
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post #6 of 10 (permalink) Old 09-29-2007, 08:46 PM Thread Starter
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Originally Posted by Hollywood Ed View Post
When I took my compressor off my 97' the clutch was rusted. Used Ford parts. Compressor, pulley, clutch. About $500. Accumulator will also be needed. Had to buy it from somewhere else. Replaced the condensor too. Should have replaced the AC muffler but did not have time. It was rusted but still doing it's primal job. The AC now works better than it has since I bought the car, which is so so. I think the car needs a bigger fan on the radiator and on the interior blower to get good results. Pay close attention to the compressor right now, because when it decides not to spin it will burn the serpentine belt right now. Burning rubber should come from the rear of the car, not from under the hood.
The AC in my '95 4.6 works well enough to freeze you out of the car. I'm not sure why you had to replace so much on a newer vehicle. The parts don't look in bad shape and the compressor will free spin allowing the belt to rotate properly it just isn't engaging the clutch due to low pressure I'm guessing.
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post #7 of 10 (permalink) Old 09-30-2007, 03:15 PM
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should be about 30-40psi with ac on highest setting maxcool but since it had R12 before not sure if you need less or more freon than what the sticker says I forget the rule of thumb for that but shouldn't be too far off. 25psi seems low though probly why its cycling on and off alot might have a leak or just low.

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post #8 of 10 (permalink) Old 09-30-2007, 03:34 PM Thread Starter
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Well I think I've finally figured it out. Even though the shop I took it to charged it up, ran it, let it sit for an hour and used both the sniffer and light they didn't pick up any leaks. Last night I took a light out to check it myself and seen about 6 places where the dye was coming through the front of the condenser. Looks like I'll be replacing that then seeing how it does from there.
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post #9 of 10 (permalink) Old 09-30-2007, 04:09 PM
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A little trick that the shop should have done in the first place, before charging the system, you need to pull a vacuum on it, and if you leave the machine hooked up holding the vacuum for about 5-10 minutes, if there is a leak anywhere in the system, your vacuum will start to drop, and then you can put some R134 in it and check for the leak. If the first shop had left the machine to hold the vacuum, they would have noticed that it wouldn't hold it, meaning there was a leak somewhere in the system. They probably just pulled the vacuum on it and charged it up right away to save some time.

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post #10 of 10 (permalink) Old 09-30-2007, 08:25 PM Thread Starter
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That's exactly what they did. The guy put 100psi in it and probably noticed that it dropped some since he didn't charge me, just told me to give him a call if the AC went warm again. I may still go back there to have him evacuate the system and recharge it and replace the condenser myself.

On the plus side, he does race a fox body t-bird with a 460 in it. I know it's punched out but I don't remember to what.
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