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A/C High psi??

Old 06-01-2010, 04:30 PM
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Default A/C High psi??

I have been playing with the A/C ever since we inherited my late FIL's XJ. Apparently he had it in 2 times for an AC leak prior (based on the receipts). For the past 2 years I would put a little coolant into the system when it would stop blowing cold air and that would fix it.

Today, I picked up a can of coolant and was about to put some into the system when I looked at the guage prior to squeezing the trigger. It wasn't low. It was up in the "red" near 100psi . So, I commence using an arrow on the filling port to releave pressure like you would to lower the psi in your tires. I get it back to the "blue" 20-40psi and it still wouldn't blow cold air.

What is my issue. Apparently I don't have a leak, but something else is causing it not to blow cold. The compressor is cycling but no ice.
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Old 06-01-2010, 07:18 PM
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ok, so do any of the connections to the dryer get cold or build up any condensation? could be plugged
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Old 06-02-2010, 08:02 AM
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Now that I released the pressure, the pressure builds to about 60psi, the unit kicks itself on, the psi then rapidly drops to 15psi before the A/C unit kicks off. Now it acts like there isn't enough coolant in it. I am starting to think that with the right amount of coolant in the unit, it runs for a few minutes (producing cold air) an then it must freeze up somewhere. When it does the psi goes up through 80- 100psi which is where it was at when I started releaving pressure yesterday. What would be causing the unit to freeze up and how can I prevent it from freezing?

I don't see any build up of frost or condensation.
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Old 06-02-2010, 11:03 AM
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Don't mess with the A/C if you don't know how it works. If the A/C is not on, you will have a static pressure of 100 psi or more on the low pressure side of the system until the compressor is turned on. You can not have air in the system for it to work correctly. Pumping in Wal-Mart cans will only add air to the system if you have not done a proper evac, vacuum, and recharge.
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Old 06-02-2010, 11:06 AM
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The compressor was on and it was up near 100psi. But it was only blowing hot air. Now I have added one can so that with it running on full blast it is at about 24psi. This is on the low side. But my theory is that I had too much in it before and it froze up the system, hence the high psi while running. After everything melted and I fired up the system, it wouldn't stay on because it would drop down below 15-20psi. Now that I put one can in it, and it is sitting at 24psi while running full blast, it stays on and the air is icy cold.
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Old 06-02-2010, 01:17 PM
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It's really hard to gauge how a system is operating or how full it is off just the low side pressure. It could still be possible to be overcharged but you won't know till you get a read on the highside, an overcharge will shorten up the life of the compressor. The pressure is best checked with windows open, the fan on full blast and the engine running at 1500 RPM at that range the high side should be 2 - 2.5 times ambient temp in degrees F for a proper charge with R-134. A secondary concern to the system would be oil, if its leaking refrigerant its lost oil too and that will need to be compensated for occasionally, and that's going to be a guess measurement at best.
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Old 06-02-2010, 04:31 PM
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The more rerfrigerant you have in the system the higher the temp will be because the pressure will go up.

For r134 a to be at 35 degrees you need 30.0 pounds of pressure on the low side.

If it air got into the system it needs to be taken to someone who can fix it. without putting a set of gauges on the system and taking some temp reading you won't know if there is a real problem or not.
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