fog from AC vents

[SoxWrx]

hey all,

I have a 2002 WRX jsut bought it a few weeks ago. when i checked it out at the dealer the AC wanst blowing cold. they recharged the AC system and checked for leaks. i have notived at times there is a stream of fog/condensation coming out of the vents. sweat does not build up on the outside of the vents just streams out in a little cloud. is this a problem????? its doesnt seem to matter how high i have the AC cranked it has happened at all fan speeds.

[azWRX06]

Yeah it's no prob all cars do it in the right conditions. I don't remember the physics behind it, but no worries.

[Darrell]

If the temperature of the air coming out of the vents is lower than the dew point, you will get "fog." It's only temporary becuase as you run the AC more and dry out the air, the dew point goes lower, thus making the car more comfortable for warm-blooded creatures with sweat glands.

This is the same principle in effect when you run the AC for a long time or on defrost mode on a humid day and the outside of the car windows get condensation.

[SoxWrx]

darrell....since you live in mass...does your rex do this? i cant say its happens everytime i use the AC but most of the time. steady stream of periodic fog coming from only the center AC vents. just want to make sure this isnt moisture caught somewhere in the system. im installing a cabin air filter today so well see if this changes anything

[Darrell]

I haven't noticed it myself as a regular occurance, but it happens from time to time in all cars. Hell, I was at the golf driving range a few weeks ago and I could see my breath as if it was the middle of winter, but the temp was about 80 ºF. Science is weird sometimes

I'll try to notice if I have any "fog" coming from my vents more regularly. Does it happen to you every time?

[blarg]

I had a similar thing happen....it was a symptom of a bad thermostat. what will happen is your AC will get TOO cold and actually freeze up until you no longer get AC...the extra pressure this produces will blow your AC compressor. I had to have mine replaced at 60k miles after my thermostat went...I thought it was nice for a while because it was blowing SO fricken cold and it was summer....but it was not a good thing. fortunately, my 100k extended gold warranty covered it.

the "Steam" is water in the air condensing because the air is so cold....it could happen on humid days anyway, but if its happening all the time, I'd have the AC thermostat checked just to be safe.

[SoxWrx]

does my 02 have an AC thermostat? if so what is it controling? duty cycle of the AC compressor? im going to need 45k service before the end of the summer perhaps the tech may be able clue me in on whats going on.

[blarg]

does my 02 have an AC thermostat? if so what is it controling? duty cycle of the AC compressor? im going to need 45k service before the end of the summer perhaps the tech may be able clue me in on whats going on.

not sure, but when I brought my car in the fourth time because the AC wasn't working and dealer replaced the compressor, he said that was the problem...there's actually a TSB about it for the 02's. Apparently the thermostat is too close to something that freezes it, and makes it stop working....if they fix it, they actually relocale the thermostat so it doesn't happen again. Not sure if the problem was fixed in 03 or 04, but its definately a known issue on the 02's.

[SoxWrx]

any ideas where i can get a list of TSBs for 02" WRXs?? i jsut fixed the wiring harness for the EVAP drain valve that was causing a CEL P0447...from the number of people ive seen with problems dealing with that it should be TSB for sure.

[blarg]

I think scoobymods has a TSB forum.