[s-cars] UrS HVAC Question

[Young, Steve]

Group collective...

Patient is a 94 S4 with 140K.  When I bought the car a few years ago, I
had a problem with the HVAC from the start.  The system would always
throw heat, unless the temp was set to "LO", at which point I would get
sufficient cooling.  Being new to the UrS clan, I bought a used
replacement CC head unit.  This was not the problem, as we would all
expect.  After more research, it seemed more like a temp flap servo.  At
this point, I had mods to do, so this went unaddressed.

Fast forward, those mods are complete and I am using the car again.  Now
I get heat all the time, even in "LO".

Fast forward more and I have all the consoles out for a SS install.  I
figure this is the time to figure this out once and for all.  I have
tested all three flap servos by cycling temp, defrost, and dash > feet.
All servos visually appear to stroke fully and operate as intended.  I
have 00.0 on channel 01.c, so no codes.  My guess is that I am out of
refrigerant.

I know these A/C systems are a PITA to work on and charge due to a lack
of a low pressure port, but is there a way to test the compressor
operation?  I assume it wouldn't engage due to a low pressure compressor
cutout.  Where is the high pressure tap so I could check for a system
charge?  Is it right at the condenser in front of the radiator?

Am I missing something in my logic?  Any help is appreciated, and TIA. 

Regards,

				TRANE
Steven Young
Local Operations Manager
Albany Office
*  Tel. (518) 724-1453
* Fax (518) 785-4359
* sryoung at trane.com

The contents of this e-mail and any attachments to it contain
confidential and/or legally privileged information, which is only for
the use of the intended recipient.  If you have received this e-mail in
error, please notify the sender by return e-mail immediately.

Furthermore, if you are not the intended recipient, you are hereby
notified that any disclosure, copying, distribution, or the taking of
any action in reliance on the comments or the contained information
included herein or attached hereto is strictly prohibited and that the
documents should be returned to the sender immediately.