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Old 12-06-2005, 01:52 PM
Matt L Matt L is offline
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Join Date: Oct 2005
Posts: 4,263
You don't say whether you intend to run CFC12 or HFC134a in your system. It matters.

CFC12 systems only need one switch, to prevent the compressor from starting if you are low on refridgerant. Some systems use a switch on the low-pressure line which also cycles the compressor, but I don't think yours is one.

HFC134a systems are required to have a high-pressure cutout switch, which will not be a stock item for a system originally speced with CFC12. But don't worry, if you buy a replacement low-pressure switch for your dryer (which is on the high-pressure line), it will also incorporate a high-presure cutout switch.

If you intend to run CFC12 and merely want to test the low-pressure cutout, just check its conductivity at ambient pressure (should be infinite resistance), and slowly increase the pressure until it conducts. Should be about 30 psig or so.

Testing whether the switch will hold pressure while in use, or whether the HFC134a high-pressure cutout works is much harder for those of us who lack 300+ psi air compressors.

Note that there's only one pressure switch on the dryer. The other device is a temperature sensor, to turn on the auxiliary fan.
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