Causes for overheat indicator? Preferred 02?

Bernie Benz b.benz at
Tue Apr 15 10:58:41 EDT 2003


Inasmuch as I replaced my last "original" 4 pin with the 3 pin many years
ago without subsiquent problems (I DFI if IAB!), I may be wrong about the
relative brand names of the two types.


> From: Phil and Judy Rose <pjrose at>
> At 9:05 AM -0700 4/15/03, Bernie Benz wrote:
>> Phil,
>> 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.  ??
> Bernie,
> Yes, the 4-pin was the original version. From what I've seen, the
> 3-pin is not sold under the VDO brandname (IIRC it's "Behlen"
> brand--perhaps made under license from VDO). The 3-pin version was
> made available as a lower-cost alternative to the original VDO--I
> don't know about the "more reliable" part.
> I don't think either version is as long-lived as we'd like.  You've
> evidently had good luck with the 3-pin model--and/or many others have
> simply had bad luck. A local shop tells me they've had many premature
> failures of the 3-pin models--perhaps just a bad batch?. If there
> actually exists is a "VDO"-branded 3-pin sensor, it might turn out to
> be more reliable than the "Behlen" brand. My most recent 3-pin
> failure was within a year (less than 10K miles) of its installation.
> The replacement I'm about to install is the 4-pin VDO. We'll see.
> Phil

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