Causes for overheat indicator? Preferred 02?

Kneale Brownson knotnook at
Tue Apr 15 13:35:52 EDT 2003

MFTS Scottmo sent me recently is the 4-pin variety.

At 09:05 AM 04/15/2003 -0700, Bernie Benz wrote:
>My experience over the years on 4 Audis, re: 3 pin vs 4 pin MFTS, has been
>that the 3 pin "passive" sensor is the more reliable of the two.  Further, I
>believe that the 4 pin "active" version was the original factory installed
>unit and that the 3 pin version was later made available by VDO to replace
>the problematic 4 pin MFTS.  ??
> > From: Phil and Judy Rose <pjrose at>
> >
> > The "low coolant/overheat" warning is a common symptom of MFTS
> > failure. If this is your situation, you'll also find that your boost
> > is limited to about 1.4 bar and your A/C is inoperative. The coolant
> > level sensor will also generate these symptoms if it is defective,
> > but that seems to happen much more rarely than MFTS failure. The MFTS
> > failure is, as you probably know, very common--especially the 3-pin
> > version. The 4-pin (VDO) version is available for the same price and
> > is possibly (hopefully!!!) somewhat more robust. Generally, when the
> > 4-pin version fails, it affects the temp gauge reading.
> >
> > Phil
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