T44 climate control troubleshooting?

[Wallace White]

Ken -

I was just discussing this with Doyt a few weeks ago on the list:

http://www.audifans.com/pipermail/quattro/20020823/060678.html

Do you have a Bentley? It is an essential help section on the climate
control system. There's no point guessing how the system should or might
behave; the book makes it all plain.

You'll find that the heater valve and recirc valve are both on a single
circuit, switched by a single solenoid valve. The normal, unenergized
condition results in the recirc flap being set to "Fresh" and the heater
valve being open. The only times these are inverted are when (1) the CC
is in Auto and trying hard to cool the car or (2) the CC is off (I think).

Reflowing the solenoid solder joints did improve the function of my
programmer, though I didn't notice any cracks.

- Wallace
   '87 5kcstq 190k

auditude at cox.net wrote:
> Today I found out that when I switch to econ from auto (lo), the hose to the heater valve loses vacuum.
>
> This after I pulled the programmer and looked at it.  I didn't see any evidence of bad solder joints.  Also,
> this programmer has a 1990 date on it, and the car is an 1988.
>
> I pulled the programmer from my '87 donor car, and it has a different connector.  Functionally, they look
> the same and I should be able to swap solenoids and the motor if I need to.  Neither motor clicks, and
> both programmers seem to hold mouth vacuum when held in the correct orientation.
>
> I'm curious as to why changing to econ from auto would have any effect on the vacuum signal to the
> heater valve.  Seems to me this is a dependent type of situation, rather than intermittent.
>
> I think I pulled the codes, channel 1 gets me 00.
>
> The parts of the airbox under the dash that I can see appear to be okay.
>
> I was thinking originally that the orientation of my programmer was wrong, and it was causing a loss of
> vacuum through the solenoids at rest.  It wasn't bolted in place and was sort of loose behind the glove
> box.  However, this morning when I properly mounted it, I still have the problem of heated econ air.
>
> Would an intermittently functioning solder joint at the heater valve solenoid coincidentally display the fault
> at the same time the control head is switched from auto to econ?  Or, am I looking at something wrong
> with the electronic signals to the programmer?
>
> I thought I would have been able to fix it more easily than this, after all the reading in the archives I did last
> night.  Maybe I should just remelt the solder on the solenoids just in case.   What voltage can I apply to
> them to check function that would be safe?
>
> Thanks,
>
> Ken
>
> On 1 Sep 2002 at 7:55, Kneale Brownson wrote:
>
>>At 12:04 AM 09/01/2002 -0700, auditude at cox.net wrote:
>>
>>
>>>On a positive note, I'm starting to get my mind around the climate control
>>>issue.  Looking at the archives,
>>>the programmer  has some basic failure modes that
>>>can be individually fixed instead of just getting a whole new one.
>>>
>>>It seem programmer-wise, I'm looking at a dirty or worn brushes (little
>>>wires) on the motor, stripped gear
>>>on the motor, broken cable end (I don't think so in my case), or sticking
>>>or otherwise faulty solenoids.
>>>Additionally, I could have a broken heat flap spring.
>>>
>>>I've already got the dash apart and the programmer exposed.  I should get
>>>some more info tomorrow.  One
>>>thing I don't understand yet is the heater valve opening at the wrong time
>>>(like bi-level with it set to 70, 100
>>>outside).  I guess this is controlled by one of the solenoids, so the
>>>motor isn't part of that (intermittent)
>>>failure.
>>>
>>>I'll be checking the control head for codes too.  Maybe I have problems
>>>with both devices.
>>
>>The heater valve is held closed by a vacuum, so if you're getting unwanted
>>heat on occasion, it's because of a loss of vacuum, isn't it?
>
>
>