overcharged AC
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Fleet Owner
Joined: Mar 2003
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From: Blue Hill Township
overcharged AC
What are the symptoms of an overcharged AC system?
I converted my 92 explorer to R134a and I believe that I might have overfilled it. The gauge set is showing just under 100psi with the engine off, but the compressor is cycling on and the air blows at about 70-80 degrees. This would tell me its low, however I have put in 3 cans which is supposed to be over full. I am confused, help!
I converted my 92 explorer to R134a and I believe that I might have overfilled it. The gauge set is showing just under 100psi with the engine off, but the compressor is cycling on and the air blows at about 70-80 degrees. This would tell me its low, however I have put in 3 cans which is supposed to be over full. I am confused, help!
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Joined: Sep 2004
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If you have too much refrigerant, duct temps will be too warm, not too cold.
The refrigerant has to be able to expand fully from a liquid to a gas in order to extract the most heat. An overcharged system leaves too much of the refrigerant as a liquid and you don't get much cooling.
100 PSI engine off sounds too high. A correctly charged R134a system runs about 70 PSI engine off as I remember it, but this is a bad way to estimate charge.
The real test is with the compressor cycling. The low side should cycle between 25 and about 45 PSI. The high side should reach a max of about 2.5 times the ambient temp. The compressor cycle should be about 7 seconds on, 10 seconds off at "reasonable" ambients (say below 85 degrees). If the cycles are longer than that, the system is overcharged. If the cycles are shorter than that, the system is undercharged.
The refrigerant has to be able to expand fully from a liquid to a gas in order to extract the most heat. An overcharged system leaves too much of the refrigerant as a liquid and you don't get much cooling.
100 PSI engine off sounds too high. A correctly charged R134a system runs about 70 PSI engine off as I remember it, but this is a bad way to estimate charge.
The real test is with the compressor cycling. The low side should cycle between 25 and about 45 PSI. The high side should reach a max of about 2.5 times the ambient temp. The compressor cycle should be about 7 seconds on, 10 seconds off at "reasonable" ambients (say below 85 degrees). If the cycles are longer than that, the system is overcharged. If the cycles are shorter than that, the system is undercharged.
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Fleet Owner
Joined: Mar 2003
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From: Blue Hill Township
Excellent info guys. I have to exchange my gauge set as the high side hose literally blew up, but I will be doing that tomorrow or Thursday. I suppose the next step is to completely evac the system and put a vacuum on it and start from scratch. 
Post Fiend
Joined: Feb 2003
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From: Eastern WA
The next step is to hook up your gauges and with the A/C on and engine running at about 1,200 rpm, bleed off a few ounces of refrigerant at a time until the low side pressure is back in the correct operating range. This assumes that the system was properly evacuated before the current charge was inserted. BTW, the pressure with the engine off is basically irrelevant to correcting this problem. All it shows is that there is *something* in there, but it doesn't indicate correct/incorrect charge.
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Fleet Owner
Joined: Mar 2003
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From: Blue Hill Township
Well, I recharged the system and its still not cooling right and the compressor is still cycling too often. I went over the factory service manual and it looks like the evaporator or orifice tube is plugged. I just don't want to sped the money for a new evaporator and another $20+ on refrigerant.
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Hotshot
Joined: Jan 2004
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From: St Louis
Originally Posted by MisterCMK
Well, I recharged the system and its still not cooling right and the compressor is still cycling too often. I went over the factory service manual and it looks like the evaporator or orifice tube is plugged. I just don't want to sped the money for a new evaporator and another $20+ on refrigerant.
Asking again. What are your readings? Whata re the ambient test conditions? Did you follow correct preparation procedures for testing?
If you want assistance, you have to answer questions that request relevent information. None of your information has been useful in understanding what is wrong.
If you just want to document whatever you're doing stumbling around, start a diary.
Steve
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From: Asheville, NC
Have you checked to see if the evaporator is plugged with leaves and crud?
Pull the blower fan and feel around inside there. Get all the dirt and leaves that you can, then using a crevice tool on a vacuum cleaner, clean out the rest of the crud. It will often make a big difference.
My '83 was loaded with leaves.
Pull the blower fan and feel around inside there. Get all the dirt and leaves that you can, then using a crevice tool on a vacuum cleaner, clean out the rest of the crud. It will often make a big difference.
My '83 was loaded with leaves.
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