First of all it is a real bummer that it has been converted.

After doing atleast a thousand of them, I can guarantee reduced performance and shortened life. The refrigerant charge is about the cheapest coponent in the system, and getting cheaper. Just isn't any reason to change anymore.

Anyway, the switch that you must get is the stock switch from about 83 on. The problem is the original earlier switch looks exactly the same and is cheaper and is widely substituted for the current part. the switch was originally just a low pressure switch designed to shut the system off when the refrigerant charge was real (I mean real) low. The later version of the switch shuts the compressor off if the pressure goes too high as in when the aux fan doesn't work. The hi pressure cut-out keeps the system from popping a cork somewhere at tremendous pressure.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician