rsbethel

2000 A4 1.8T
My A/C blows hot air when I am driving in the city and cold air when I am on the highway. I know that the problem is the auxiliary fan, which is not working. I tried fixing the problem replacing the fan but did not work. There is not power (electricity) going to the fan. Could somebody help to figure out the problem?

Thanks in advance
Raul

ChooChooNongNongHead

I believe that you had just replaced the fan for nothing. Did you at least jump it or bench test the old fan?

First thing that I'd do (did on my car) is VAG it. Run through the diagnostics to let it run the various tests... one of which is kicking the fan on.
Make sure that your compressors clutch is engaging when you turn the A/C on (it probably isn't though since you're getting warm air)

Why isn't your compressor running? Well, it could just be that you're low on freon so check that first... it's the cheapest fix. Without enough freon, your clutch will not engage / saving you from a compressor failure... when your clutch isn't engaging, your fan will not come on.
If the freon IS low, add some to spec and find out why you're leaking freon.

Okay, your freon is up to spec and your A/C still isn't blowing cold. This may be a faulty outside temp sensor, the relay under your dash, a bad a/c pressure switch (behind pass side headlight) or at worst, your compressor and/or clutch have failed... not cheap and a PITA to replace (at least on my 2.8)

If everything seems okay, the last step would be to try to jump the compressor. You'll have to find that wire on your car. Mine (2.8) is connected near the Power steering reservoir It's a single wire with a green connecter. There are a few wires so make sure that you have the correct one and make SURE that you have enough freon. You'll have to look close at the center of the pulley to see if the clutch is engaging. If it's not engaging, start saving your pennies for a new one. If it is, and everything that I mentioned checks out, I don't know what to tell you... come back and ask the forum again.

Oh yeah, I have one belt on my 2.8 that runs everything but I guess you have a separate belt for your A/C. Make sure that's okay.
Good luck and start diagnosing things before replacing parts.

WHOOPS, I reread your post before replying. I see that it sometimes works on the highway? Hmmm, I don't know then... make sure your freon is good, VAG the AC system and make sure that your belt is good and tight..
I'll reply anyway incase any of my ramblings made sense.

tobin

<ul><li><a href="https://forums.audiworld.com/a4/msgs/2568867.phtml">Read his post</a></li></ul>

rsbethel

Thank you very much for this post. But could somebody tell me the locations for the 4 possible problems:
1.bad A/C pressure switch
2.bad high speed fan relay, J101
3.bad fan relay fuse, 5Amp S51
4.bad fan fuse, 40Amp S42

rsbethel

Thank you very much for this post. But could somebody tell me the locations for the 4 possible problems:
1.bad A/C pressure switch
2.bad high speed fan relay, J101
3.bad fan relay fuse, 5Amp S51
4.bad fan fuse, 40Amp S42

tobin

1. I don't know
2-4. Remove the lower dash panel (the whole piece below the steering wheel). The relays are both on the main relay panel, about a foot above the clutch pedal. The fuse is below this panel, and it is the only 40 amp fuse there. Do you have a voltometer? I purchased and installed a brand new electric fan only to find out that it didn't work.

rsbethel

I would like to appreciate your advice; I was able to find the problem (the 40A fuse) was bad. Again, thank you very much and God bless you all.