1994 S4 - a/c cut out

["R. Cummings" <cumm@flash.net>]

>Subject: 1994 S4 - Door seals, a/c cut out
>
....
>Another annoying thing is that the a/c cuts out when the outside
>temperature drops below 5 degrees centigrade.  Is there a good reason
>for this?  Is there a way to stop it happening because it causes the
>windows to start steaming up when the car is full of people.
>
>Philip Ross
>Scotland
>

Fred Munro was of course on the mark. If the A/C system ran below 32f the
moisture would freeze on the evaporator blocking the air flow. In addition,
the switch needs some differential built in. If it turns off at 32f, it will
not turn back on until 41f. In effect, under 41f it doesn't run. If the
differential is set too low, the system can short cycle which affects the
life of the clutch and compressor. It is also difficult to manufacture those
switches with a low differential. So, Audi engineers did not decide to turn
it off because they thought it wasn't needed.

Bob Cummings 87 Coupe GT