RE: My '87 Quattro blows! (Hot air)

["Buchholz, Steven" <Steven.Buchholz@kla-tencor.com>]

>   I am the proud owner of a new (to me) '87 Quattro and I am having a few
> minor problems with it.
>   I think there is something amis with the thermostat or cooling system. I
> took the car for a 400 mile checkout drive over the weekend. The car
> performed very well except for two things:
> 
> 1) The car blew very warm air through the far left and far right vents the
> entire time. This is even with the temperature control guage all the way
> to
> the left (cool). The center vents seemed to blow cool air the entire time.
> I had the selector on vents, not floor. The outside air temp. was about 60
> degrees F. The reason I suspect a thermostat or cooling system problem is
> because there was a large variation in the engine temp. reading on the
> dash. It seemed like the car wasn't keeping itself very cool while
> climbing
> or in city traffic even though the outside air was relatively cool. I'm
> afraid of what it will do when it gets warmer. The temp guage also blinks
> on and off when I go around corners when I just start the car. A friend
> said there are sensors to detect the coolant reserve level but I checked
> the reservoir when the car was cold and it seemed full. The air coming
> from
> the side vents was so warm that I had to close them and open the sunroof.
> 
> Any Ideas?
> 
It turns out that Audi chose to have coolant flowing through the heater core
almost always ... using a pair of regulating (blend) flaps to control the
temperature.  These flaps are controlled by a "Bowden Cable" from the AC
"Programmer" behind the glove box to the blower box.  There are two dominant
failure mechanisms, one being the gear that drives the cable having teeth
break off, and the other intermittent poor contacts in the potentiometer
that provides the feedback as to where the flaps are currently set.  I'm
pretty sure that for the former your best hope is to find a programmer in a
wrecking yard that has a good gear on it (Tony Lum will also have some good
information on rebuilding the vacuum switches on the programmer, which you
might as well do at the same time ...).  I have heard that the fix for the
latter involves installing a fixed value resistor between the center contact
on the pot and one of the end taps ... I've never done this so I don't know
what R value to use or to which end the resistor needs to connect (I'm
pretty sure that its in an Audi TSB).  

Blinking temp gauge probably means that the coolant level is low in the
reservoir ... which might imply that there is a coolant leak somewhere ...

It turns out that the temp sender for the gauge is another one of those
common failures on the 5ks ... your descriptions of what you see don't quite
fit the standard failure mode, but you may want to look into testing the
"Multifunction Temperature Sender" attached to the bottom of the flange that
attaches the upper radiator hose to the head.  You might also want to check
that the radiator cooling fan is working properly ...

> 2) The windshield wiper fluid motor isn't working. Digging seemed to
> indicate that fuse #12 was the fuse connected to the motor. is this
> correct? This fuse seems to be fine. I haven't put a DVM on the motor yet.
> 
... do you know for sure that the pump isn't working at all?  The common
failure IME is that the pump wears to the point where it is no longer able
to build up enough pressure to open the check valve that is in the supply
line.  I have disassembled the valve, removed the guts and reassembled on 3
5ks so far ... and this has fixed the problem every time.  If the pump truly
isn't running, then as you suggest it might be a fuse or the switch on the
column ...

Welcome to the land of the Audi 5000 fixers Jeremy!  Have fun!  Once you get
the car sorted out you should look into installing a boost upgrade ...
highly recommended ...

Steve Buchholz
San Jose, CA (USA)