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Re: 3-terminal (not 4) multifunction thermoswitch

Hairy green toads from Mars made Phil and Judy Rose say:

> Recently I posted about erratic A/C in my '89 100. The A/C cools very well
> when the compressor cycles on, but once in a while--inexplicably--it
> refuses to cycle on for extensive periods (hours). A local Audi A/C
> mechanic concluded that freon level was OK, and  his guess ("guess", since
> A/C was working OK at the time) was that the multifunction thermoswitch was
> defective and sometimes sends a spurious overheat signal which keeps the
> A/C off.
> I passed this info along to the Audi mechanic who had done repairs on the
> vehicle before I bought it. He stated that in the past he had sometimes
> installed non-OEM thermoswitches, which had only 3 terminals instaed of the
> 4 in the OEM version. The use of these 3-legged switches he later found to
> be correlated with A/C non-functioning. Sure enough, a 3-terminal switch
> had indeed been installed in my Audi. He'll be giving me a free replacement
> switch (OEM).
> Has anyone encountered this problem with the use of a 3-terminal
> thermoswitch? How come everything seems to work fine *most* of the time?

I've had the 3-pin in my '89 100Q for almost 3 years without problem.
I put one in Angela's '90 90Q20V about 1.5 years ago, without problem.

I don't believe the 4-pin is made any more; it has been superseded by
the 3-pin (the 4th pin was for a separate ground connection).


Andrew L. Duane (JOT-7)			duane@zk3.dec.com
Digital Equipment Corporation		(603)-881-1294
110 Spit Brook Road
M/S ZKO3-3/U14
Nashua, NH    03062-2698

Only my cat shares my opinions, and she's too heavy to care.