Re: Climate Control

[steveb@falcon.kla.com (Steven Buchholz)]

> I'm having intermittant problems with the climate control in my '87 5ksq.
> When it's working, it seems to work fine (aside from the fact that my A/C
> is just about shot), but on occasion it seems to get "stuck".  I just got
> back from the grocery store and all the way there and back it would blow
> nothing but full heat, despite the warm temperature outside.  Even setting
> it to "Lo" produces heat on these occasions.  Turning the climate control
> completely off results in a very small amount of hot air coming from the
> front defrost vents and directly at my feet.

If you've got air coming out somewhere other than the defrost vents then 
you probably are not having a vacuum problem.  This is unfortunate, since 
finding and fixing a vacuum leak is much easier than having to dig into the
system.  
> 
> I've only had my (first, yay!) Audi for a few months, and still have a lot
> to learn about the electrical and mechanical systems.  I'm going on a trip
> to Toronto in a couple of weeks, and dread the thought of having heat
> blowing the entire 12 hr drive! :(  The former owner of the car said he had
> this problem intermittantly too, and his mechanic was unable to isolate the
> problem.  Any insight would be greatly appreciated. :)
> 
The best thing for you to do is to get a copy of the Bentley manual ... it 
has a very comprehensive troubleshooting section, and the CC in the car has 
built in diagnostic capabilities that are easy for at home service.  If you 
think about the fact that you are planning to take a 10 year old car on a 
trip the Bentley could come in handy should the unexpected occur.  My Audis 
have never left me stranded on my road trips ... but I've always got the 
manuals and tools in the car just in case!  My newest Audi is 9 and my oldest
is 19 ...

It turns out that the system has coolant flowing through the heater core 
most all of the time and it adjusts temperature by blending hot and cold 
air.  My recommendation to stop the hot air when the system breaks is that 
there is a vacuum controlled heater valve mounted near the back of the 
head and firewall.  If you apply a constant vacuum to this valve it will 
close, which will stop the coolant flow to the heater core.  This may 
provide some relief for you.  I've been tempted to rig an override switch 
on my car to allow me to control if any hot coolant gets to the heater 
core on hot days.  

Good luck ... and have a safe trip!
Steve Buchholz
s_buchho@kla.com
San Jose, CA (USA)