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92 celica GT - A/C clutch won't engage, relay is good and clutch is good..

5816 Views 8 Replies 4 Participants Last post by  93celicaconv, 
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hey everyone, i am a newbie on the forum. i am Ron, and I own a 92 Celica GT with 32,000 original miles on it. the car has been garage kept and is my weekend driver. the car is all stock with the exception of a cold air intake.. yesterday the A/C stopped blowing cold on me. I have a background in computers, so i figured i could troubleshoot this myself, but i have found the wiring diagrams very confusing. Anyways, i thought i would start with the easy stuff, such as testing the A/C clutch relay, fuse, and the A/C clutch itself. All three test good. i tested continuity across the 10 amp fuse under the passenger's side kick panel and it tested good. i pulled out the a/c clutch relay in the engine bay relay box by the compressor, put 12 volts to the coil side, and it would click on. just to be sure, i swapped out another spare relay i have for when the door motor went out on me, and the relay is the same part number, so i tested it, plugged it in, and still no clutch engagement. now.. i tested the clutch by jumpering pins 3 and 5 on the relay box, and the clutch engages and the a/c cools the car. the pressure on the low side is 35 psi with the clutch engaged.

so what do i test now? the relay is good, the fuse is good, and the compressor is good... what other components will cause the clutch to not engage, and how do i test them??

thanks in advance for the help

Ron
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You have a 3-way pressure switch in your low-side refrigerant line. It is open when the pressure is below 27 psi and when above 350 psi (don't quote me on those values, but they should be close) and closed with the pressures are in between. Perhaps this switch went bad on you.

Otherwise, other than a wire open circuiting somewhere, it sounds like the A/C compressor should be active when you turn your A/C system on.
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93celicaconv said:
You have a 3-way pressure switch in your low-side refrigerant line. It is open when the pressure is below 27 psi and when above 350 psi (don't quote me on those values, but they should be close) and closed with the pressures are in between. Perhaps this switch went bad on you.

Otherwise, other than a wire open circuiting somewhere, it sounds like the A/C compressor should be active when you turn your A/C system on.
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can anyone post a picture of the location of this pressure switch, so that i may troubleshoot it?
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RobMilkshakes
You have PM.
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RobMilkshakes said:
You have PM.
Click to expand...

thanks for that diagram rob...


ok.. so i did that, tested the switch, the pressure switch is good as when i jumper it, the idle changes instantly as if more fuel is being added to the mixture.

ok so far: the pressure switch is good, the relay is good, the fuse is good, AND, if disconnect the postive lead on the compressor connector and apply 12volts to it directly, the clutch engages. however, if i just jumper the two wires( 3, 5) with the relay out, the clutch won't engage. the a/c fan engages when i do this, since the the clutch relay turns on the a/c fan relay, but no compressor. I am guessing at this point that the a/c amplifier is repsonsible at this point since it seems to get feedback from all of these devices?? am I missing something?

getting closer....
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R
i have a 91 celica gt and have HAD problems with a/c just recently. i noticed you said it has 32,000 miles on it and wondered IF you have had the TSB for the air conditioning done way back in the 90's???? this could be part of your problem.....
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ROCKLAND TOYOTA said:
i have a 91 celica gt and have HAD problems with a/c just recently. i noticed you said it has 32,000 miles on it and wondered IF you have had the TSB for the air conditioning done way back in the 90's???? this could be part of your problem.....
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could be.. what were the details of the tsb? do you have a link to it online?
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R
SSC PO1 is the bulletin i found. kinda old now and hard to find.....
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The recall was for a leaking expansion valve. The fix was to replace it and recharge the A/C system. If the expansion valve had leaked, you wouldn't have refrigerant in your system. I don't think this is your problem, because you said you have 35 psi on the low side with the compressor running. It seems like your refrigerant pressure is about normal for a working system.
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