'84 4kq - temp guage & warning light ?s + thermo switch ?

Ben Swann bswann at worldnet.att.net
Mon Nov 18 10:05:45 EST 2002

Follow-up - Among other minor issues, I found the connector for the temp
switch had been put on backwards.  The "idiot-proof" connector was broken
which allowed this to happen.  I plugged it in properly, and now the temp
guage works properly and the overheat light doesn't come on.

I still am having problems with the car running properly/consistantly.  The
thermo switch for ECU control was definately bad.  I replaced with another(
used but seemed in spec) - ran great, and then the problem reappeared
later.  I tried yet another switch, a (used also seemed to be close to
spec) but seem to get rough running at some point in the warmup cycle.
 Just wondering if I should replace outright with a new and expensive
sensor, or there might be something else I have missed.

I have been over the engine thouroughly - replaced vac. lines, checked
injectors/repl. seals,  New throttle body/idle switch, added ground wire
Battery(-) -> Valve cover -> IM -> front chassis.

The car runs like a scalded cat when not having its little problem, but
sometimes it runs rough, has no power and won't rev over 2k, sputters and
coughs.  Does this sound like a thermo switch issue?


On Wednesday, November 13, 2002 4:01 PM, Tony Lum [SMTP:tlum at flash.net]
> At 11:21 AM 11/13/02 , Tony replied to what Ben asked:
> >I have been getting this '84 4000 quattro back on the road for its new
> >owner.
> >
> >It is (CIS E) model.
> >
> >Where is the sending unit for the water temp. guage?  Is that contained
> >the same two prong switch on top of the cooling neck below #1 cyl.  Do
> >these/does this pass current to ground or ??  Bently is not clear, but
> >is what diagram indicates.
> Yes, that's it.  The one on the bottom is for the CIS computer temp
> >Reason for question(s) - the temp guage is not registering temp and the
> >overheat warning light starts to glow but only dimly when hot/fan
> Probably needs replacement.
> >The oil pressure warning light goes on at around 2500 rpm too with
> >cool, and when warm, many of the lights start to glow with the oil p.
> >light when engine revved.  Wiring problem with the instrument cluster,
> >multiple sensors going kaput?
> I'd check all grounds from the instrument cluster to chassis.
> HTH,
> - Tony
> lots of I-5 Audis

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