HVAC diagnostic for 1990

[RELAYER@aol.com]

I noticed everybody giving advise on how to do  a diagnostic check on a 5KCSQ
auto air system.  Does anyone with a BENTLEY manual for the 90/COupe Q know
what the diag codes for that system are? mine is screwing up (not
recirculating the air, switching between defrost & vent) and I swapped the
digital control modules between my 2 audis, with no difference, so it must be
something else like the vacume hose control unit that is in the passenger
side dash.  Thanks for any advise!!!!!!!!!!

Christian Long, Orlando, FL
1990 90
1990 COupe Q