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Old 07-31-2008, 12:31 AM   #10
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Join Date: Jan 2006
Location: NYC
Posts: 44,439

2003 L-Series 3.0L Sedan
Default Re: AC blows warm when idling

Originally Posted by turbobuick33 View Post
My gf has a 95 sc2 and the AC blows cold while driving but when coming to stop or when the car is idling the AC becomes warm and not cold. What would cause this?
You're either gonna' be a hero or jack*** to your gf (there's just no middle ground unless the car is taken to the a/c shop) if you do the following; If you make a real honest effort to look real hard for evidence of a leak and can't find any, you should be able to use a refill can of R134a with dye (only). Do not use any miracle sealer! If you don't spend the time to look for the source of the leak and refill, there's no guarantee of this refill lasting a day, a week or the rest of the season. A/C systems are sealed and pressurized and not to be refilled every year, week, or monthly. The fastest and easiest leak is right at the service port where refrigerant is injected into the system. Cheap store can refills with plastic quick couplers may cause an incorrect connection and/or seem like a connection without actually depressing the valve stem (that allows refrigerant into or out of the system). It can also lead to complete discharging of the system when these quick couplers are disconnected and the valve stem doesn't re-seat properly. Just the little things to keep in mind for those that think its so easy to simply refill and drive away. Yes, it can be that simple but when things go wrong they go wrong in a big way unless you're prepared ahead of time.

Being prepared may mean spending money to buy a real screw-on can tap that pierces the sealed R134a can and allows precision amounts of gas/fluid into the system along with a real hose with a real metal fitting that can be used over and over. Its your choice and your risk when working around airconditioning systems. Servicing a/c systems can be done, when done correctly, but if using cheap equipment and disaster occurs......................

Buy a dial type thermometer to insert into the center vents, a/c on medium fan speed, all windows open, the car preferably in the shade with a fan blowing into the radiator. Have the can of R134a w/dye attached to the hose, purged the hose, and attached to the only fitting that will accept the low pressure hose fitting - the rear end of the compressor. Here's where the seriousness of a/c work cannot be stressed enough. If a refill can were somehow attached to the HIGH pressure side, the valve opened and the compressor running, AN EXPLOSION CAN OCCUR! ! ! The compressor (discharge side) can output as high as 250psi+ (the rated safety vent valve will only open at around 450psi!) so incorrectly hooking up on the wrong side can and will result in disaster, injury, and a very rude awakening of inept, poorly informed, untrained DIYer's forcing a fitting when fittings were designed to prevent this from occurring. Don't take this personally but if you don't know which fitting is which (I'm addressing anyone and everyone reading these threads) and don't make the effort to find out then you're better off leaving a/c work to a pro. Its that simple.

Careful co-ordination of regulating engine speed with or without someone else behind the wheel, E-brakes applied, in PARK or NEUTRAL can ensure a safe working environment otherwise carelessness can lead to..................

With the R134a attached to the service port (suction side) and the valve closed, start the engine, turn on the a/c (with the compressor running), run the engine up to 1500rpm and hold it there while opening the valve so the refill can will dispense refrigerant. Monitor the interior temps while injecting refrigerant. Keep the can upright and as the can becomes very cold, have a small pail for very warm water to partially submerge the can into to transfer the warmth to the can contents. As soon as interior temps approach 45F stop injecting refrigerant by shutting off the valve. Watch the temperature dial for the next few minutes as the a/c system stabilizes. If the temps stay, this can left this way (depending on outside temperatures) and everything disconnected or carefully dispensing a few ounces more of R134a and closing the valve to watch the dial thermometer. Overcharging here will lead to higher HIGH-side pressures and begin to raise the cold temperatures instead of lowering it. Carefully feeding a few ounces and halting the feed while monitoring the dial thermometer will show whether or not temperatures will drop. Be very careful not to add anymore R134a than necessary. Don't try for lower temperatures by injecting more refrigerant. 40F is the absolute lowest with a car standing still and a fan blowing into the radiator as this isn't driving at highway speeds at higher rpm. Both will lower interior temperatures as a/c efficiency improves at 2000rpm. Don't "I'll just throw in another half can for reserve in case of a small leak or so I don't have to do this again for another year" make the excuse to overfill. Use just enough and stop, period. Give away the rest of the can's contents to someone else or leave it on the shelf as there isn't any shelf life of refrigerant. It stays fresh as long as the gaskets and valve seals work, preventing any refigerant from leaking out. Your gf's car should be good to go.
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