[200q20v] Fun with boost problems.

Bernie Benz b.m.benz at prodigy.net
Mon Dec 17 16:03:28 EST 2001


You did not differentiate between the two types of MFTS out there.  Of
course, you must be talking about the 3 terminal, electrically passive type
that has superceded the 4 terminal, active type.


> From: Brett Dikeman <brett at cloud9.net>
> Date: Mon, 17 Dec 2001 15:02:19 -0500
> To: QSHIPQ at aol.com, digitaleopard at hotmail.com, 200q20v at audifans.com,
> quattro at audifans.com, s-car-list at yahoogroups.com, audi20v at rennlist.org
> Subject: Re: [200q20v] Fun with boost problems.
> At 8:51 AM -0500 12/17/01, QSHIPQ at aol.com wrote:
>> Ron:
>> The MFTS could be working correctly, but the wiring to it could be faulty,
>> btdt.  The only 2 items that trigger the temp light (this applies to S cars,
>> 5k/200, 90q20v and late euro urq's <not us urq) as well) are the MFTS and the
>> antifreeze level warning light
> Something else to consider...when "frobbed" a MFTS will sometimes
> mysteriously start working again, which is why they can be a
> mysterious item to troubleshoot.  I remember when I had my old 5k,
> that I unplugged the thing, looked at the connector, looked fine,
> plugged it back in...everything started working.  Little while later,
> temp gauge goes dead.  Bump the bottom half of the sensor, starts
> working again, etc.
> Open a dead one up sometime.  Takes a while, mototool with a heavy
> duty grinding wheel, is a must...but they're pretty neat inside, and
> you can see why they fail, at least temp gauge-wise.  Saw a ring of
> the brass part off near the bottom, maybe about 1/8th to 1/4 of an
> inch up from the lip, that lip is what holds the whole thing together.
> The temp switches are more of a mystery; they're basically relay-like
> in design, and there is a wax expansion piston setup(the tip of the
> sensor is full of wax) which presses against the set of contacts; one
> pair closes at one level, then a second close at a higher level.
> I don't remember, off hand, if I noticed any immediately obvious
> reason why the overheat part would fail, which is weird, because it's
> not exactly an uncommon problem.  I don't think I have the stuff
> still around. Maybe if I have an old sensor, I'll saw it open and
> have a look-see.
> B
> --
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