AC Controller Q

[Matthew Caprio]

FYI-
I have (partially) diagnosed this same problem in my car, and it turns out
it is related to a low voltage problem locally at the AC Programmer (the
vacuum switch box).  I have monitored the signals to the solenoids, and they
sometimes drop from their constantly regulated 11.75v down to 9.5v.  I think
that the 12v to the programmer is regulated somewhere, probably the AC head
(the box with the settings in the dash) and for some reason the supply
voltage to it drops slightly enough for the regulator to "fall out", and
have the output drop to this ~9v level, at which point the solenoids might
lose their force enough to become unreliable.  In my case, when this
happens, if I tap on the box the proper vents may again be chosen.

My car system voltage is not low >13v, I have monitored it during these
events, so I have not figured out what is causing the low voltage at the
programmer.  Perhaps my lead to the AC head is bad, or a connection is bad
at one of the connectors, or my head is going bad?...  I will test it more
thoroughly in the future, and let you know what I find.

In the mean time, I have installed a jumper hose arrangement to avoid my
programmer and select my vents "manually" putting the air reliably to the
top/center vents.

Good luck.

Matt


----- Original Message -----
From: "Steve Sherman" <spsherm at attglobal.net>
To: "quattro" <quattro at audifans.com>
Sent: Saturday, August 11, 2001 12:31 PM
Subject: AC Controller Q


> One of my 5K's is giving me fits in trying to fix the AC Controller (the
> vacuum switch part).  The symptoms are the usual air coming out of the
> defrost vents when it should be at the dash vents.
>
> In the past (with other 5Ks) this has not been that big a deal. Yet
> nothing I try on this car seems to work for long. I have tried a couple
> of controller boxes (both have been checked for hose leaks internally).
> I have checked the lines between the controller and the right vacuum
> actuator and they are good, no leaks and they do pass air.  The vacuum
> actuator does work (will move when vacuum is applied).
>
> When I work on the system I can ususally get things to work before I put
> the under-dash back together, yet a day or two later it is back to not
> working.  The only thing I have not  checked is the actual vacuum level
> at the controller.  Anyone know what vacuum should be on the black
> "input" line at idle???  However since other vacuum actuated things seem
> to move OK (like the air recirculating door) I have been assuming that
> the vacuum level is OK...
>
> Any ideas of where else to look on this one??
>
> TIA
>
>
>