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OT- Car A/C question

W

Wesley Stephens

Member
I have a 92 Buick Century that has been converted to R-134 refrigerant. The car has a lot of miles but is in decent shape and is a solid farm/work car. The issue with the A/C is that it works fine when the RPMs are up but at idle and slightly higher it does not cool. What has me stumped is even at idle the clutch on the compressor is engaged and it is turning without kicking in and out like you would expect to see if the freon was low. It will put out cold air within seconds of revving it to about 1500 rpm and works fine at highway speeds. I have not had many vehicles with air conditioning because I tend to drive old, worn out stuff but here in hot, humid SE NC it is a wonderful thing from late March to November. Does anyone have any ideas? I have talked to several folks and have gotten a lot of head scratching. Does anyone have any ideas? I would greatly appreciate the help.
 
I will assume it has a fan clutch or fluid driven fan? I have seen these go bad and not pull enough air at idle, also make sure the condensor and radiator fins are straight and clean, most GM's A/C systems I have delt with the compressor turns almost if not always at idle at least, just a thought or two
 
it's a little front wheel drive economy car of sorts and has an electric fan. I've seen the fan running, but it may not be coming on when it should.
 
Sounds like a classic case of a worn out compressor.Have someone hook a set of gauges to the high and low side.Depending on ambient temp,the low(suction) side should be approx 35-45 psi and the high(discharge) side anywhre from 150-300 psi.

By increasing the engine speed,the compressor runs fast enough to achieve these pressures.The low pressure cycling switch should cut off power to the compressor clutch at about 25 psi,but I doubt the compressure is pulling it down anywhere close to that due to wear.
 
the compressor is a variable displacement and will not cycle if low. the suction line on compressor should be cold 30-40 f and the discharge on compressor will be hot. hook up a set of gauges should see 40 lbs on low side and 140-200 on high side depending on outside temp. could still be a low system.
 
I'll get someone to check the pressures. I'd hate to have to buy a compressor, but I'll be using the car as a daily driver through the summer so I may go ahead and bite the bullet if that's the problem.
 
Clean the condenser coil first, you may have to seperate it a little to get between it and clean there is usually a lot of debris between the radiator and the condenser. Checking pressures before you do it is a waste of time. Been there done that. I put a compressor on a tractor last year and the pressures went nuts and it didn"t cool. I moved the coil out and it was plugged solid. I bent a copper line to make a spray wand to get up between the coils. It cost you very little to do this first.
 
R134A has different characteristics than R12, so it's typical for conversions to have poor cooling at idle. They make an "automatic adjusting" orifice tube for conversions that will improve the idle cooling performance. The part itself is only about 20 bucks, but of course the system has to be evacuated to change it out.

Go to Rock Auto and look it up for your Buick. They offer several versions varying in price from 10 to 45 bucks; I don't know why the ten buck version wouldn't work just fine. (Sorry, I can't give you a direct link, the Rock web site doesn't work that way.)
Rock Auto
 
Did you take pressure readings? That complaint is not uncommon with 134-A if it is underchaged. 134-A will leak out where R-12 was and didn't leak because the molecules are smaller on 134-A.
 
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