Pressure Switch, EXP. Valve, Evaporator, Service Fittings

Pressure
Switch:
The pressure switch now uses compatible sealing materials, as well a coated control diaphragm suitable for R-134a. Check the parts for green labels. The label will indicate if the switch is suitable for R-134a use, or both R-134a and R-12 use. Lack of the green label is a good indication the switch is compatible with R-12 only.

Expansion
Valve:
The R-134a system expansion valve uses a different opening pressure. This enables the valve to work more efficiently with the new refrigerant. An expansion valve designed for use in R-12 systems installed in a R-134a system will permit insufficient expansion into the evaporator and yield poor cooling.

Evaporator:
The R-134a system evaporator is virtually identical to R-12 units, except the R-134a compatible units use no copper. The temperature sensor (to prevent evaporator icing) has not changed. An R-12 evaporator should not be used in an R-134a system.





Service
Fittings:
In order to prevent accidental charging with R-12, the R-134a systems use unique quick-disconnect service fittings on the vehicle. Recycling equipment for use with R-134a has hose ends specifically designed for these fittings. The high side and low side fittings are different sizes (pressure side larger) to assure proper hookup. Any difficulty in connecting service equipment may be an indication of refrigerant/equipment incompatibility with the vehicle's system. Always carefully ascertain the type of refrigerant used in the vehicle's system before performing service. Labels in the engine compartment, typically on the top of the fan shroud, will detail which refrigerant is used in the air conditioning system. Service the vehicle with compatible recycling equipment ONLY. Attempts to adapt and use incompatible service tools will destroy both the vehicle's air conditioning system and the service tools.