Werid A/C Problem???

[supercharged666]

I got a 1998 Trans-Am and when I turn the A/C on max it blows ice cold air for about 30min. Then it seems like it doesn't want to blow cold air any more. I have to keep stepping it up a noych on the blower speed and then when I'm finally on the highest blower speed it still seems like it doesn't want to blow and it barely cools the car off. Then I can turn the car off for a half an hour and come back and it will be fine, until i use the a/c for another half an hour. Anyone have this problem. I was thinking it might be a problem with the blower motor maybe over heating from being on so long but it doesn't do it when i turn it to heat. I can have the heat running for hours and the blower speed will remain the same. Anyone ever have this problem.

[badbrad]

Sounds like your A/C unit is freezing up, getting too cold and freezing blocks the flow of Freon or what ever. I know at my house a/c was low on freon/ and I kept putting the thermostate lower and lower and eventually the a/c unit froze up. Turing it off for a few hours it thawed out and worked fine. Sound slike your car is doign the same, working for a while, freezing up and thawing after turned off, then it is working again.

[2001NBMZ28]

I agree, sounds like it's low on refrigerant and the evaporator is freezing up. Sometimes you can hear a low "crackling" noise as it thaws when turning it off and putting the selector on vent.

[supercharged666]

I agree with you guys that it does sound like it is freezing up, but if your low on freeon wouldn't you have warmer than normal a/c tempertures? I should check the charge of freeon in the system. If its low i can charge it up. Its just that it blows ice cold when i first turn it on, just seems to me if it were low on freeon it would blow kinda warm when you first turn it on?

[2001NBMZ28]

R134a isn't a "coolant", the change in pressures and from a gas to a liquid state is what gives the cooling transfer. For instance in your home AC if your filter is clogged or the evaporator (indoor) fan isn't runing at speed and not allowing for the transfer of heat the evaporator will start cool, then rapidly ice up. Same principle. In your case sounds like the blower motor is trying to pass air through a clogged (iced up) evaporator. Sounds complicated but basically once the evaporator ices up the fan is blowing air on an ice cube in both cases, resulting in luke warm air and no cooling. When the refrigerant gets low you'll get the best temperature transfer right up to the point it starts freezing up, then goes downhill. If the pressure gets too low, the car will shut the compressor off and not come on at all.

[supercharged666]

Hey thanks for explaining that. Makes alot of sense. Gunna go check the charge of freon and get back to you.