ac turns off at idle
TECH Addict
Joined: Mar 2004
Posts: 2,336
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From: Fat Chance Hotel
You can't really check pressures without gauges. First thing to do is buy the gauges, because if you start guessing with the pressures you can easily damage the system. Then it will cost you much more than $100 to replace something like a compressor.
If you're low on refrigerant, there is also the possiblity you have a leak. The system will normally leak at an extremely slow rate so is your car is older and never had the system serviced, then you just might be low.
If you're low on refrigerant, there is also the possiblity you have a leak. The system will normally leak at an extremely slow rate so is your car is older and never had the system serviced, then you just might be low.
TECH Addict
Joined: Mar 2004
Posts: 2,336
Likes: 0
From: Fat Chance Hotel
Hook them up...very easy. Start the car and turn on the A/C. The see what the high and low side pressures are. Low side should be ~40-45psi and high side should be (considering you're in FL) ~180-200psi. Those numbers are rough estimates, but you should be relatively close to that with respect to ambient temperatures. Don't measure with the car running in the garage...too much heat to deal with. Make sure you're outside.
I noticed this picking my car up at the airport, the cycling
while I was idling & loading bags. It only did it at cold idle
and not after I drove, the A/C was on when I left it. I could
see it being high side pressure cutout with the fans being
off (cold) and the condenser being uncooled, the refrigerant
would just stack up as vapor w/ pressure head. Once the
engine gets hot it is running the fans or rolling enough for
the condenser to work.
Or something. Like maybe that no-plates Borla of yours
usually drowns it out.
while I was idling & loading bags. It only did it at cold idle
and not after I drove, the A/C was on when I left it. I could
see it being high side pressure cutout with the fans being
off (cold) and the condenser being uncooled, the refrigerant
would just stack up as vapor w/ pressure head. Once the
engine gets hot it is running the fans or rolling enough for
the condenser to work.
Or something. Like maybe that no-plates Borla of yours
usually drowns it out.
I would say hook up some gauges and see what your pressures are doing and that will tell you if your low or whats going on. A good way to tell whether or not your system is undercharged is checking your static pressures. Hook your gauges up with the car off and leave it sit for a while with the A/C off to let your pressures equalize. But after you do that both your high and low side pressures should within about 5-10 degress of the ambient air temp. So if its 80 outside both your gauges should be reading between 75-85, and if they are your system is fully charged and your problem lies elsewhere then low freon. I would say do this first. And also when you have the gauges hooked up on the car keep it between 1500-2000RPM. thats where it should be to do a good performance check on your a/c system and plus since your compressor isnt stayin on your pressures will be fluctuating a lot at idle and you wont be able to make anything out. But do your static pressure check and if that checks out alright come back with the readings you get at 2k and then we can diagnose your problem further.
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Originally Posted by TheBlurLS1
Some cars that the a/c cycles on and off have a temp sensor on the return air so they will cycle much like the a/c in your house does if you stick it on 72*.
Yeah a thermostatic cycling switch they are usually mounted around the evaporator somewhere but I dont think our cars have them. Correct me if im wrong.
If you get a set of manifold gauges with both compund and high pressure gauges there will be a fitting on your accumulator(the aluminum canister looking thing behind the battery. That is your low side service fitting, normally its the blue hose and gauge. And the high side service fitting(red hose and gauge) is located on the liquid line coming out of the top of your condensor and going to what looks like inside the car. The fittings are different sizes so your only going to be able to hook them up one way so dont worry about hooking up the wrong gauge to the wrong fitting. Make sure you screw in the valves all the way on the hoses once you have them clipped onto the fitting, otherwise you wont be getting accurate if any readings.
Another plan:do nothing for a week and if you have a leak it will lose more freon and the compressor won't come on at all.
When I used to charge cars(not professionaly) I would have to jumper the low pressure switch
as you couldn't put freon in unless compressor was running! Low would be my guess for sure!
When I used to charge cars(not professionaly) I would have to jumper the low pressure switch
as you couldn't put freon in unless compressor was running! Low would be my guess for sure!
On The Tree
Joined: Jan 2006
Posts: 105
Likes: 0
From: Waco, TX
Theres a low pressure switch on the accumulator unplug it and jump the two connectors with a paper clip the clutch should come on, thats the easiest way to test the switch. If you know you have plenty of R134 in the system and the compressor is off until you jump the wires you know the switch is bad. The switch is just there to keep you from burning your compressor up when you have a bad leak.
Originally Posted by MIKE_84
Theres a low pressure switch on the accumulator unplug it and jump the two connectors with a paper clip the clutch should come on, thats the easiest way to test the switch. If you know you have plenty of R134 in the system and the compressor is off until you jump the wires you know the switch is bad. The switch is just there to keep you from burning your compressor up when you have a bad leak.
Im Reluctant To Say Its Low Pressure Becuae The Propmels Is Occasional And Not Every Time The A\c Is On
I Am Having Alternator Problems And They Seem To Coinside With The A\c Problem So Im Gonna Fix The Alternator Problem And See If The A\c Deal Goes Away
I Am Having Alternator Problems And They Seem To Coinside With The A\c Problem So Im Gonna Fix The Alternator Problem And See If The A\c Deal Goes Away
Originally Posted by DrivenWS6
I would say hook up some gauges and see what your pressures are doing and that will tell you if your low or whats going on. A good way to tell whether or not your system is undercharged is checking your static pressures. Hook your gauges up with the car off and leave it sit for a while with the A/C off to let your pressures equalize. But after you do that both your high and low side pressures should within about 5-10 degress of the ambient air temp. So if its 80 outside both your gauges should be reading between 75-85, and if they are your system is fully charged and your problem lies elsewhere then low freon. I would say do this first. And also when you have the gauges hooked up on the car keep it between 1500-2000RPM. thats where it should be to do a good performance check on your a/c system and plus since your compressor isnt stayin on your pressures will be fluctuating a lot at idle and you wont be able to make anything out. But do your static pressure check and if that checks out alright come back with the readings you get at 2k and then we can diagnose your problem further.
Wrong, wrong, wrong. Pressure does not equal volume. Checking static pressure will only tell you if it has any refrigerant at all in it. Refrigerant pressures fluctuate with temperature, not volume. You can have a canister with 30 lbs. of refrigerant in it and one the same size with 10 lbs. in it, both will read the same pressure if they are the same temperature. Do you have a T&P chart for 134a? If not, how do you know what static psi would be at 80 degrees?
Anyway, just go to autozone and buy the 134a that comes with a gauge, $16 last time I bought one. Its an idiot gauge, but it works. Or go to a local shop, they will check your charge for pretty cheap. Some of the local places here will check and charge the system for like $40 up to 2 lbs.