The AC in my car suddenly stopped working. I don't think the compressor is
moving at all. There is no change in idle speed or sound from the engine
when I turn the AC/heater unit on and off. There is a fuse marked heater/AC
or something like that but it's not broken and I guess if it was, the heater
unit would not work at all. I think there is an electrically operated
"clutch" that connects the compressor to the drive belt. Could this thing be
on a separate fuse? How do I find this "clutch" and the wires that controls
it? Anyone know how I can troubleshoot this?
If your AC has a display, you will be able to pull the fault codes from it
by pressing a combination of buttons. Unfortunately, I don't know what these
will be for your model but a search on the internet might help you.
First check that the AC compressor belt hasn't snapped - it'll be down the
front of the engine.
Second engage the AC & then feel the AC lines - (usually aluminim looking
things routed around the side of the engine bay) one should go cold pretty
quickly & you should see condensation. If it does go cold then the AC is
working & try changing your cabin pollen filter - that worked for me on an
A4 a couple of months ago when we thought the AC had died.
If the line doesn't go cold then either the compressor/compressor clutch has
packed in or you have a big leak & have lost all your AC fluid (in which
case don't drive the thing too far). The fluid also acts as a lubricant &
without it the compressor will sieze if it hasn't already.
If the AC system lost pressure, the low pressure switch would cut the power
to the magnetic clutch and the pulley would just freewheel - part of
recharging a system when it is under vacuum is bridging the low pressure
switch to get the compressor to run.
Chances are, if you turn the system full cold and you don't hear the
occasional click of the clutch engaging on the compressor, and with the
engine off you can turn the compressor by hand (you can do it so long as the
clutch isn't welded to the pulley) will indicate that the AC has probably
lost enough pressure to activate the LP switch. If you can find the
location of the switch - it's a wired pressure transducer teed into an AC
line - and bypass it (for a short time to avoid burnout) to make the clutch
engage and run the system, then the system has lost some pressure.
1987 Audi 5kTQ
1980 Audi 5k
1962 and '64 Auto Union DKW Junior deLuxes
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Thanks, Ill give it a try tomorrow. I also noticed today that the electric
radiator fan is running even though the car is cold. It should not do that
should it? If some faulty sensor tells the computer the engine is hot, could
it turn of the AC in an effort to keep the engine cold?
The fan will run all the time the AC on ( * )display is shown on the
panel.. On our 97' model the fan ran although the LP switch had detected
low pressure and disengaged the compressor (clutch open).
So your problem most likely is a normal loss of refrigeration gas. Most
workshops will fill up the system for less than 2' NKR.. The prosedure
takes about an hour as it involves complete drainage, vacumtest and
The vacumtest however will not always detect small leakages. So if you
loose gas within a few weeks a check using tracing liquid and ultraviolet
light will be necessary. Got this for free, as I filled twice in a month..
had to change one line due to pittings under a plastic shrink fit hose at
a suspension point..
Using Opera's revolutionary e-mail client: http://www.opera.com/mail /
On newer cars it's not a switch but some kind of pressure transducer. So you
have to find out what resistance that will make the clutch engage.
But my car is at the Audi garage now. Hope they can figure out what's wrong.
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