[V6-12v] Radiator Fans not working

Tom Christiansen tomchr at ee.washington.edu
Tue Sep 21 15:13:08 EDT 2004


The fuse is labeled S42 on the schematic. I don't think there are fuses 
other places than in the box under the hood. There might be an in-line fuse 
as someone suggested. It's supposed to be a 60 A fuse, so I doubt it's in 
the fuse box. Follow the wires from the battery to the fan. You'll find it 
(if it's there).

Last time I had relay trouble (or thought I had), I found out that a lot of 
the relays are identical. So you should be able to take one known-good 
relay and replace one of the fan relays with it. See if that gets the fans 
going. To test the relays, apply 12 V to the relay coil and measure the 
resistance of the contacts. You can see which terminals goes to what on the 
little schematic on the top or side of the relay.

I would make sure that the fans work before doing anything else. Disconnect 
the fans from whatever they are connected to and measure the resistance 
between the two wires going to the fans. If it's a dead short, try rotating 
the fan blade. If that changes the resistance, the fan should be good. In 
that case, hook it up to the battery (be prepared for sparks) and see if it 
runs. On my car there are two fans connected in parallel. If one dies 
(shorts out) none of them will run.

If the fan works, then it's a fuse, relay, or control problem.

I don't know if there's a method for checking the fan thermal switch. But I 
would imagine that the switch would trip if you dunk the switch in boiling 
water. That could  be verified with an ohmmeter.


At 05:18 AM 9/21/2004, T. Jackson wrote:
>Thanks for the list.  I did find one other fuse that I had missed which is
>in spot 20 I believe and it is a 30 Amp fuse for Fan speed 1.  This fuse
>also seems to be fine.  I also looked for fuse S42 but could not find it.
>Is this fuse located under the dash or under the hood?
>With respect to the relays, how can I test that these are not the problem?
>Know Audi they are likely to be expensive to replace so I don't want to
>attempt to buy them unless I absolutely have to.
>Are there any 93-95 90 owners in the Greater Toronto Area that are willing
>to help with the swap?
>-----Original Message-----
>From: v6-12v-bounces at audifans.com [mailto:v6-12v-bounces at audifans.com] On
>Behalf Of Tom Christiansen
>Sent: Monday, September 20, 2004 10:45 PM
>To: T. Jackson; 'V6 12V Audi Mailing List'
>Subject: Re: [V6-12v] Radiator Fans not working
>The fan speed is controlled by a thermal switch located on the starboard
>side, bottom of the radiator just above the drain  plug. I forget how many
>speeds the fan has but I think it's three. The different speeds are set
>with a resistor pack located on the port side sub-frame. It's pretty easy
>to find if you trace the wires from the fans. It looks like an L-bracket
>with a couple of wire taps on it.
>So there are a couple of possibilities for failure:
>1) The fans themselves.
>2) The two relays driving the fans: The one at position 18 (high speed) and
>the other at position 11 (low speed).
>3) The resistor pack.
>4) The thermal switch.
>5) Fuses S15 (25 A) and/or S42 (60 A).
>The fan is supposed to run at full speed when the A/C high pressure switch
>engages. I would assume it does so when the A/C is running. The fan on my
>1994 90S normally turns on at low speed when the temp gauge reaches about
>straight up (whichever temperature that is).
>If you click "wiring diagrams" in the Bentley manual, then select your
>model year, and select "manual climate control" you should be guided to
>page 102 in the manual. It has the relevant schematic.
>At 05:06 PM 9/20/2004, T. Jackson wrote:
> >I noticed this morning while sitting in traffic that my car was running a
> >little warmer than normal.  After a while the traffic cleared up and I
> >started moving so the car temperature stayed nominal until I got to work
> >forgot about the abnormal temperature reading.  On the way home after
> >sitting in traffic I noticed my temperature gauge slowly approaching the
> >120C mark while my oil temp was around 130C!  I managed to get the car
> >moving again and cool enough to pull over and check the fuse box.  The fuse
> >seemed to be in good shape and the label on the box indicated that it is
> >shared with other items like turn signals and wipers which all appear to be
> >working.  Before continuing the drive on the open road I did a quick check
> >to see if there were any disconnected wires or harnesses and I couldn't see
> >any.  It was much too hot to go prodding in the engine bay so I saved
> >the potential 3rd degree burns and I will take a look at it in the morning
> >when it's much cooler.
> >
> >
> >Does anyone have any ideas as to what I should be looking for?  Is it
> >feasible to test the fans by applying 12V from the battery to the connector
> >(where ever it is)?
> >
> >
> >BTW, the car is a 1995 Audi 90 Quattro.
> >
> >Thanks!
> >
> >
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