[s-cars] Fan works,

Sat May 18 14:30:27 PDT 2013

 Hold up on the below Tom....  MFTS does not report to the guage on the S car, that co-function was taken away from that sensor after the 1991 200.  The MFTS reports an overheat condition (115C+    IIRC) to the temperature avitar on the instrument cluster.  The same overheat avitar is tied to the coolant expansion tank level sensor (MFTS and coolant level are parallel signals).  So if the coolant float is sinking, the 'overheat' light could light, OR it's the MFTS.  Disconnect the coolant tank sensor plug is the test for that branch of the circuit.  If you still have the light, chances are better than 90%, in addition to a bad rad temp sender, you *also* have a bad MFTS.

I don't agree that the rad temp sender no worky, means the radiator is bad.  That sensor is used in all sorts of audis from 1985>, and I replace those regularly on all different chassis when they fail.  What usually goes with the rad temp sensor is the heater core, not the radiator.  BTDT. BTST many, many times.

Lastly, I claim anyone that deletes their primary viscous cooling fan and runs just the aux fan on an S car, best replace that radiator temp sensor *again*.  I say that move is just plain crazy (I'd say dumb, but I'll refrain).  Even the v6 cars use 2 cooling fans, the v8 uses a viscous and an aux (with 2 temp senders on the v8, one in the radiator, one in the coolant neck)....  Further, since most aftermarket suppliers of the S car aux fan, supply the 360W fan as the direct interchange replacement, not the 500W fan that came in an S car from the factory, many S car owners are already airflow challenged.  I could certainly take the argument that one replaced the viscous with 'another' electric fan.  But I wince hearing educated folks on this list claiming that only the S car aux fan is adequate for a turbocharged car.  I may remind you that doing this delete massively reduces the reserve cooling capacity Audi built into the S car cooling design.

HTH, and my .02 arbitraged through the peso.

Scott J

-----Original Message-----
From: Tom Green <trgreen at comcast.net>
To: s-car-list <s-car-list at audifans.com>
Sent: Sat, May 18, 2013 2:26 pm
Subject: Re: [s-cars] Fan works,

Slow down a little here, Jim.  I would tackle these one at a time.  I  
know you need to get any parts ordered, so that sort of depends on  
your confidence in these parts.  The MFTS seems to be doing its job  
reporting to the coolant temperature gauge.  I would check the  
contacts under the rubber protective boot to make sure they are not  
corroded or otherwise in bad shape, or the sensor leaking.  It could  
be coated with deposits from the water inside.  Same with the  
connector for the coolant tank level sensor.

I echo the comments of Scott J, FWIW.  If the radiator is original, it  
is common to see hard water deposit sludge completely covering the fan  
sensor.  If shorting the sensor wiring contacts produces results, it's  
time for a new sensor, and IMO,  a new radiator.

Tom '95 S6
          '95.5 S6 avant
Knoxville, TN

On Saturday May 18, 2013, at 11:53 AM, "Jim Fleischer" <jim at almgt.com>  
wrote:

> Alrighty then!  I may have misunderstood something earlier regarding  
> some testing, but.....
>
> Was able to get the fan going at both speeds jumping the terminal  
> wires from the radiator sending unit, so looks like I'll be  
> replacing that.  However, Scott mentioned something about the MFTS  
> triggering the overheat warning and suspending A/C operation.  These  
> are my symptoms as well.  Could both have stopped working at the  
> same time, or one take out the other?  Or is it just the MFTS  
> malfunctioning?  Am I best off just replacing both?  Besides the  
> usual AutohausAZ, GenuineVWAudiparts, etc, any good source?  Thanks!
>
> I'm sure there are other things I should replace while I have the  
> coolant out.....I've got a couple of plastic coolant fittings, etc.   
> Feel free to chime in with other suggestions.....
>
> Thanks for all the help and patience.....I learn something new  
> everytime!  Totally appreciated!
>
> Best regards,
>
> Jim Fleischer
> '95 urS6 avant
>  ----- Original Message -----
>  From: Qshipq
>  To: Jim Fleischer ; s-car-list at audifans.com
>  Sent: Friday, May 17, 2013 10:12 PM
>  Subject: RE: [s-cars] Fan works, just doesn't come on.....(Formerly  
> Electric Fan not working)
>
>
>
>
>  Pull the belly pan and look for the temp sender on the DS radiator  
> end cap.  Pull the 3wire connector off temp sender.  On the wiring  
> plug side jump positions 1-2 med speed fan then 1-3 high speed fan.   
> If this operates the respective fan speeds replace radiator sending  
> unit ---  you describe classic radiator fan switch failure. If you  
> have an overheat warning the a/c should shut down which means the  
> aux fan is also shut down.  IIRC on the S-cars that overheat warning  
> is triggered by the MFTS and/or low coolant level - that circuit is  
> T'd together.
>
>
>  Could be the MFTS is bad too...  Or because your rad fans aren't  
> functioning the MFTS is actually doing its job?
>
>
>  Bet this car fails the rad temp sender check.
>
>
>  HTH
>
>
>  Scott J

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