The freon pressure switch (mounted on the receiver/drier)that M-B used on W124 vehicles was prone to leaking and has gone through a couple of revisions: 124 820 59 10-05, to 124 821 36 51, and, presently, 124 820 83 10. However, even this newest version seems to have problems, invariably leaking through the small set screw located at the top of the switch, in the middle of the two contacts.

What is the purpose of this screw and is it sealed with an o-ring? Can this screw be turned so as to stop an existing leak and then covered with a glue or sealant to prevent releaking? Does rotation of the screw alter the freon cutoff pressure setting?

Turning the screw will change the calibration of the switch. I have only had a handfull of them leak. I think if yours is leaking too many times, you could have a high pressure situation or contamination.

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Benzmac:
Donnie Drummonds
1991 GMC Syclone
ASE CERTIFIED MASTER AUTO TECHNICIAN
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