I had the a/c Compressor go out on my Jetta, I had the Compressor, Receiver Dryer, Condenser and Expansion Valve Replaced. The problem I am having now is the two engine fans seem to run erratically. They both come on low speed when the a/c button is pressed. I remember before I had the A/C work done the fans used to kick into a 2nd speed often and the a/c would get ice cold, now these fans do go into a 2nd higher speed but they don't do it as often or when you need them to. When they do go faster the a/c cools down nicely, but sometimes they will stay at low speed for a while and the vent temps will start climbing into the mid to high 50's and be there for a while then sometimes the fans will kick into 2nd speed and the vent temps will drop into the high 30's low 40's and stay there for a while then for no reason they kick back to low speed and the temp of the a/c will go up 20 degrees. I have even noticed them kick on at freeway speed and saw vent temps as low as 35. It is just so erratic. The compressor is engaged at all times so it is not the compressor cycling. I have watched the fans at idle act this way and watched what happens to the vent temps. What could be the problem? Could it be the Air Conditioning Pressure switch that is on the line that runs by the firewall. Would this cause this erratic variance in temps and fan behavior or is there another switch that controls the fans?
That car has a variable compressor that is controlled by internal pressure. It is sort of a chicken-egg situation that the fans may not be running because the compressor is not compressing as much as it should. Watching the pressures when it is not working would be necessary in the diagnosis.
With the car moving at freeway speed there is plenty of air being pushed through the condenser even with no fans at all. If you're getting inconsistent cooling on the freeway it is going to be something else besides the fans.
The fans are working I am just talking about the fans going from low speed to 2nd speed.
The fan speed is controlled by high side pressure though. Right now without measuring the pressure you can't tell if the fans aren't speeding up because the pressure is not increasing, or if the pressure is increasing but the fans don't respond.
That is true, I don't personally have a gauge but I will get one. At what pressure should the fans go to second speed?
Usually it's set up to trip at 250 to 300 psi.
You will need an actual manifold gauge set to do this test, not just a cheap charging hose with a low side gauge that is typically found in front of the counter at mass market parts stores. Ordering from the site sponsor is of course recommended, but any pro-oriented parts store and some of the chain stores have them if you ask.
Edited: Wed August 14, 2013 at 11:31 AM by mk378
I am going to order one. Just one more quick question is the pressure switch the one that changes the fan speed? This might be hard to answer but at what ambient temperature or situation will a a/c system typically get into the 250 to 300psi range. Thanks so much
I'd think anything above about 90-95ÃÂ°F should work.
Edited: Wed August 14, 2013 at 1:31 PM by webbch
I have not received the gauges yet to get the pressures but today we had a hotter day than the weather we have been having. It has been a fairly cool summer here usually temps in the hi 70's to low 80's every day and this is where the a/c is not work very good maybe 50 degree vent temp at best. Today it was mid 90's for the first time in a while and the A/C mostly blew ice cold I had vent temps between 38 to 42 most of the time as low as 36 on the freeway. I drove for a hour but every so often I can hear and feel something cut out randomly, which I have observed as the fans going to slow speed and the vent temps will rise 20 degrees to about 60 degrees for a minute or two and then it will kick back in and be at the 38 to 42 range for a while, it only warms up once every 5 minutes or so.
It is odd to me anyways that the a/c would blow colder as the outside temp increases, this is the opposite of every other car I have ever had, other cars would be a couple degrees warmer on a really hot day. what do you think?
basically what would cause the a/c to get colder as the outside temp rises?
It sounds like your new compressor or TXV are acting up, causing it to abnormally reduce cooling sometimes. I doubt it is strictly related to outside temperature. Pressure readings will tell the tale.
You don't think I could be that the Pressure switch went bad from the compressor imploding that is what I was thinking. I went and had pressures checked. Hi side was 230 Low side 34 at 78 degrees. Vent temps were between 48 and 54 with engine fans going from 1st to 2nd speed it would change speed for a few seconds then come on at second speed and stay for a little while, pressures stayed the same.
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