When you say "it gets very cold" are you sure that you are not just icing up the evaporator inside the car and the air flow slows down a little until you notice it is getting warm in the car.

The compressor will shut off if the low pressure switch senses that the evaporator is satisfied as it will be not getting heated from warm air passing through it.

If so, you may need to adjust the low pressure switch upwards or change it out completely.

There is a screw between the prongs that can be turned just a tiny biy bit (do not remember which way)to keep the evaporator from getting to cold and frosting up.

If switch is defective you can replace it straight-on as it just unscrews and there is a valve core under it to stop any leakage.

Hope this helps!
Phil

Yes you are correct, idiot lights that this idiot reads.
--
1993 240, 1992 240GL, 1985 240DL Wagon, 1983 240DL

And a /93 should have the R134a system, not an R12? I think the R134 system operates at higher pressures.


R134a systems also circulate the lubricant needed by the compressor with the refrigerant. if the compressor runs without refrigerant coming through the inlet, it will quickly die, so R134 systems have a pressure switch on the low pressure side of the system. If the inlet pressure drops too low, the compressor kicks off.

There's also a pressure switch on the high pressure side that kicks it off if the pressure gets too high.

Given your symptoms it's *probably* the low pressure switch turning the compressor off. And that's likely due to one of two things:
1) A slow leak, system doesn't have enough freon, once the compressor has pumped a lot of it over to the high pressure side the low pressure side doesn't have enough, so it turns off the compressor until enough circulates back through to the low side.

2) A stuck/plugged expansion valve - the gizmo that makes the pressure drop part way through the system,, so the liquid freon boils and sucks up heat in the evaporator to make cold air. If those stick or get plugged, or the reciever drier gets clogged (or, for that matter, frosted up with water contamination) then freon can't flow through the system from the hi to lo sides, and eventually, the low side gets starved, or the high pressure switch calls off the party.

You need to get good PSI pressure readings both at rest (after the hi and lo sides have equalized, car shut off for a while) and while running to see what's really going on.
--
'63 PV544 rat rod, '93 Classic #1141 245 (now w/16V turbo)