[s-cars] Re: outside temp sensor MIA - WTF?

[Douglas Landaeta]

I am throwing a 7.1 on the HVAC OBD and have ordered the "the fresh air
intake duct (G89, according to Bentley)" temperature sensor. Part 4A0 820
539. I have not looked at where it fits yet, but it seems close to the
pollen filter and blower motor. The symptom is hard to recognize unless
you've been in a correctly working car - inside temp. runs a little colder
than you set it and the floor vents have very little output, so your feet
are a bit cold, manual override works just fine - so it's not the dampers.
It may even be just a wiring fault, but having the part on hand before the
digging may save some time and trouble.

Doug L

Originals follow:

Ian added...

Bentley says there are four temp sensors working on the AC. The interior
ones are on the dash (G56), and at the headliner level (G86). The exterior
one (G17) is the one you've discovered to be missing. The fourth is in the
fresh air intake duct (G89, according to Bentley). HTH.

-Ian Duff.

Bob sez...

There is a fresh air intake duct temp sensor, and a fresh air blower ambient
temp sensor in the windshield cowling area.  I think the system compares the
readings from the bumper mounted sensor and the intake temp sensor.  Strange
though that the outside temp display would all of a sudden start reading
properly without a sensor there.  Have you checked the climate control
diagnostics?  It should tell you if you have a fault with any of the other
sensors.

Bob

> Bob and gruppe,
>
> I found my problem. The wire and plug are there but the sensor is MIA!
> Last night we joined some friends for an early season BBQ and I let
> Donna drive der neu S6. Being an S4 driver herself, she immediately
> noticed that I was "wrong" and should have my climate control system
> set to "Auto". "Oh yeah, this is the right way, it will do it all
> itself - just set the temp."  "Alright honey I said..."
>
> Well, I can tell you that the outside temp reading said -40 below again
> right when we started to drive, and since she switched it over to 67
> deg on Auto that S6 did every thing in it's heating powers to make the
> car 67 deg thinking that it was -40 below outside! Holygesh, the heater
> was on max! Dropping it to LO fixed it, but was then cold. The outside
> temp sensor IS somehow connected into the climate control system. We
> figured this out quickly enough and I started to fritz around with
> trying to make the A/C go on. No go - it still thinks that it is -40
> below outside - why would you need the A/C? Then, the outside temp
> guage started to climb back out of Siberia (after 10 min) and level out
> to a normal +43 deg. Hmmm, just then the A/C snowflake appeared on and
> the system stabilized. I turned off the A/C and everything was still
> good. Inside temps were right.
>
> After finding a MIA front sensor this morning, what I don't understand
> is how could the whole system finally do a sub zero drop, then come
> back to normal? There must be another sensor somewhere lurking in
> there. Maybe I'll ask the hidden pollen filter where it is...
>
> Thompson
>
> On Wednesday, March 26, 2003, at 10:47  PM, Bob Rossato wrote:
>
> > *This message was transferred with a trial version of CommuniGate(tm)
> > Pro*
> >> I can't for the life of me find the outside temp sensor in the front
> >> anywhere. Give me some pointers as to BTDTs.
> >
> > The temp sensor is mounted pretty much smack dab in the center of the
> > front
> > bumper.  Open the hood, stick your hand behind the bumper and reach
> > towards
> > the front.  You should feel it there, though may not necessarily be
> > able to
> > see it.  If you look through the center bumper grille you should see it
> > though.  As I recall, a -40 reading is a sign of a disconnected, or
> > maybe
> > failed sensor,
> >
> > Bob