Receiver/dryer Sensor Description
> Does anyone know what the two sensors on the side of the
>receiver/dryer on an '87 S4 are for?
>One has two quite large connectors from the top, and the other has two small
>connectors on the bottom.
>I assume one is a low pressure switch - what is the other & which one is
The one that looks like an oil pressure switch, mounted on the side or the receiver/dryer, is the low pressure switch. This one cuts off the compressor if the freon pressure gets too low due to a leak.
The one mounted on the stem on the earlier cars is a freon temp switch, to turn on the aux electric fan when the freon gets hot.
On the S4 and later cars, the freon temp switch is replaced by a freon pressure switch to tell the computer when the A/C compressor is working, so the computer can control the two electric cooling fans.
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