850 ECC - problem (electronic climate control)

1996 855 TDI, left hand driven, with ECC and automatic gearbox. I haven´t
investigated the behaviour of my climate control in complete depth yet, but...
sometimes, today again (outside temp about 22 degrees Celsius with sunshine),
left and right controls on the ECC set to 22 (=72 F)degrees Celsius, I find the
left side driver´s air outlet to blow out too warm air, the right hand outlets
blow out definitely colder air with air con turned on. When I closed the right
side outlets, my side started to get cold air, too. When I turned aircon off,
fan manually at max to dry the system before parking, I got heated air out of my
left hand outlets today, even when I turned down the temp control knob to the
minimum of 16 degrees Celsius for my left side. Never any blinking lights
indicating error on the ECC as much as I follow it. When it was really hot this
summer, I do not remember that this phenomenon occured. I usually had fan and
air distribution on auto and air con on, for the last 5-10 min air con off, fan
manually at max for drying the system. When I change the air-distribution from
auto to the different positions, the correct action is taken, as much as I could
determine. So I assume think the ventilation damper motors are working ok.

My guess is that the temperature control damper motor on the left=driver's side
or the left air duct temperature sensor might be malfunctioning. Remote idea:
Interior temperature sensor on left side malfunctioning. Another guess is
trouble in ECC computer city.

My plan so far: go to the automobile club and have the ECC error code read out
if there is any and they have the equipment. Self-adjustment of damper motor
limit positions in test mode 4, if they have equipment for that.

If no clear info from that, then disconnecting the battery and having it like
that over night. Is the ECC disconnected completely by turning off ignition?

I have had the the windscreen replaced last winter because of damage to glass
surface, no accident. Could anything be damaged when changing it?

Thankful for any input on how to tackle the problem with simple means

Viktor Weisshäupl, Vienna, Austria