Converting, General
Background
- In year model 1992, R134a refrigerant was introduced. R134a is a chlorine-free refrigerant which does not damage the ozone layer in the atmosphere.
- A method has now been developed which makes it possible to convert A/C systems from R12 refrigerant to R134a. This conversion basically consists of draining R12 from the system, and then flushing it with R12 repeatedly so that the old refrigeration oil is removed and then changing the desiccant container and charging with new compressor oil. Finally, R134a is charged.
- Conversion can be carried out using various equipment. Three different alternatives are described in these instructions. Equipment common to all three alternatives is a refrigerant bottle with two cocks, charging equipment for R134a, about 10 kg of R12 refrigerant for flushing the system and R134a refrigerant for recharging it. In addition, special adapters must be used when connecting the A/C system.
- Conversion of the A/C system has mainly been developed as an alternative for Saab owners who wish to have a refrigerant which does not damage the ozone layer. At the same time, it should be pointed out that the refrigerant industry is more and more switching from R12 to R134a, which may, in the long term, affect the availability and price of R12.
Converting, general
- When converting from R12 to R134a, the compressor oil must also be changed. The properties of the R12 mineral oil in the system mean that it does not mix with R134a and does not therefore lubricate the compressor sufficiently. In its place, ester oil should be used in A/C systems which have been converted to R134a. Note that this only applies to converted A/C systems. In A/C systems which have been filled with R134a during factory production, PAG oil, and nothing else, should be used. However, it is not sufficient to simply fill the system with ester oil. The old mineral oil must first be removed. Otherwise, it will form an insulating layer in the evaporator and significantly decrease the performance of the A/C system.
- In order to minimize the risk of chemical reactions and loss of cooling performance, at least 90% of the mineral oil should be removed before the new refrigerant is charged.
NOTE: That the total quantity of mineral oil in the A/C system can vary (as the system may have been repaired without the correct quantity of oil being added).
- When refrigerant is emptied from the A/C system, mineral oil remains in the various parts of the system. In order to remove at least 90% of the mineral oil, the A/C system must be flushed with R12 using a special method.
- During flushing, the A/C system is first emptied of R12. Liquid R12 is then charged on the high-pressure side of the compressor The refrigerant circulates in the A/C system and is removed through an adapter in the compressor's oil filler connection. When flushing, it is important to remove all restrictions in the A/C system and equipment, such as Schrader valves, so that there is free flow. The expansion valve is held open by heating its sensor to max. 50 °C.
- As the system is working with refrigerant in liquid form at a pressure lower than normal operating pressure, the mineral oil will float on top of the refrigerant. The oil flows around the A/C system with the refrigerant and is removed through the oil filler connection at the top of the compressor
- In order to reach oil which is pressed up into pockets, the fluid level should be raised and lowered during rinsing. When level is' lowered, the oil comes down from these pockets. Fluid level can be seen in the sight glass and can also be read as pressure changes on the pressure gauges connected to the suction side of the draining station. When converting to R134a in markets with a hot climate, an extra radiator fan can be fitted in front of the condenser on the Saab 9000 in order to increase cooling performance.