Air conditioning is cold, but stops blowing

[Beej]

Good afternoon. I am hoping someone has knowledge of this problem.

I have a 2002 PT with a little over 100K miles on it. Recently, the volume of air coming out of the vents will drastically decrease when driving on the highway. The air that comes out is still cold, but it just trickles out instead of blowing as normal. Yesterday, I discovered that I could "fix" this problem by opening the windows of the car for a time. The A/C will resume normal functioning for 10 minutes or so and then quit. The A/C works normally in the city. This is a highway problem only.

Also, when the problem is occurring, I can crank the A/C fan to the highest setting and hear it blowing. This will increase the airflow a little bit, but not much. Additionally, I can hear a strange sound from the passenger side dash.

I am guessing that this is a vacuum problem, but I am not sure where to look. I have recently spent $1000 on repairs (starter, steering column, etc.) and would like to try to fix this myself. Any help would be appreciated.


Thanks.

[CREWZIN]

I can guess that it might be the pressure switch located on the accumulator. It happened to mine. The system actually gets so cold it freezes up and given the right circumstances, it unfreezes and starts to work again for awhile.

Just a guess.

[Beej]

Thank you. I will look into that.

[85_305]

But he said the air is still COLD.. but the fan isn't blowing it out strong enough... right? I dont think that would be the switch if thats the case

[Beej]

85_305,

Yes. The air is still cold. Even when its volume is diminished from the vents, the air that is coming out is still cold. When the problem occurs, it's almost like the air is being diverted away from the cabin. The fan is still turning, but it sounds like it is blowing behind the passenger side dash.

[CREWZIN]

When my cycling switch went bad, the compressor stayed on all the time (not cycling) and "I think" it was the evaporator that was icing up and blocking air flow into the interior. A couple minutes of not running or on the heat cycle would melt the ice and allow air to flow again. I could also hear the fan blowing but hardly any air was coming through.

Besides, I said it was just a guess. It may not be his problem but someplace to start.

[Beej]

Is the cycling switch something I can change myself, or would I lose freon when I remove it from the accumulator?

[CREWZIN]

There's no freon (R134) loss when changing the cycling switch but there's a tiny "O" ring at the bottom that is easily squashed and ruined when tightening the switch down.

Again, I'm just taking a guess because of what happened to mine. Ask around some more to see if someone else has any advise.

[85_305]

Originally Posted by CREWZIN

When my cycling switch went bad, the compressor stayed on all the time (not cycling) and "I think" it was the evaporator that was icing up and blocking air flow into the interior. A couple minutes of not running or on the heat cycle would melt the ice and allow air to flow again. I could also hear the fan blowing but hardly any air was coming through.

Besides, I said it was just a guess. It may not be his problem but someplace to start.

Hmmm interesting. I dont see how the actual air-flow would be hampered from the ac not pumping out cold air. I would think it would just flow out warmer air. But what your saying seems to run hand-in-hand with what this guy is experiencing. So that would certainly be a good place to start.

[bjorneffsteen]

I have this same EXACT problem. Or, rather "had" because now the compressor does not appear to come on. Which I define as not hearing the click followed by cold air. My A/C used to blow really cold, then all of a sudden the force would decrease by 99%, just a trickle of cold air. I could turn the heater on for a few minutes, then switch A/C back on and it would work for a while. Now, the A/C doesn't work. Is it that little switch, or is there a climate control unit behind the dash? Is there a non-expensive way out of this problem?