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post #1 of 4 (permalink) Old 06-04-11, 07:43 PM Thread Starter
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1990 Ford Crown Victoria A/C 134a Pressure

Hello,
I have a 1990 Ford Crown Victoria wagon that blew a seal in the a/c compressor. Bought new compressor, accumulator, orifice tube, new o-rings, added oil to components.
Checked for leaks with a compressor, ok; vacuumed system, and it seemed to hold the vacuum. I am in the process of charging with 134a, can anyone tell me what are the proper high and low pressures for this car?
Currently, I have the pressures at 20 psi on the low side, and 200 on the high side. Today's temperature was 77 degrees F. I am getting cool air but the compressor is still cycling on and off especially when I first start the car up.
Is this ok or should the compressor always run continuously?
Any replies would be appreciated.
Thank you

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post #2 of 4 (permalink) Old 06-04-11, 09:04 PM
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Re: 1990 Ford Crown Victoria A/C 134a Pressure

Just put the proper amount that the system calls for. The low side is usually around 30 when the compressor shuts down.

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post #3 of 4 (permalink) Old 06-04-11, 09:48 PM
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Re: 1990 Ford Crown Victoria A/C 134a Pressure

For a car that old, it probably does and probably should have a cycling clutch system and the on and off cycling of the clutch is normal. High side pressures are kinda complicated to figure out because they can be affected by humidity and barometric pressure as well as temperature. I was recently taught a generic rule for high side pressures. Take the ambient temperature and add 100 to it. The sum is an approximation for what your high side pressure should be in PSI. Do not treat this sum as an absolute must have pressure. Remember that the high side pressure can be influenced by other atmospheric conditions. From where I'm sitting, your numbers look good and the compressor seems to be doing what it's suppose to be doing.
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post #4 of 4 (permalink) Old 06-12-11, 06:50 PM
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Re: 1990 Ford Crown Victoria A/C 134a Pressure

A 1990 should have had R-12 in it originally, how much R-134a did you put in? The rule of thumb is put 75% of R134a that the system used with R12. I think your pressures are high, and you overcharged it. Whats the temp at the center register?
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