[200q20v] Fun with boost problems.

[Brett Dikeman]

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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