Originally posted by Terry Haines:
The lube carried within each type do not mix too well and can cause compressor problems....
What Terry said. Also, R-12 is slightly denser (heat carrying wise) than r-134a. This means more r-134a has to be circulating to give the same performance. In short, the conversion will have less capacity than the original. The correction to this is a faster turning compressor at a given engine RPM and larger orifices or expansion valves in the system.
Having said that, a properly flushed and cleaned system will work and the reduced capacity is noticed mostly at idle and low speeds, something some people don't mind. It is not a DYI job. If you do not recover the old refrigerant you are violating the law. If you are not certified to work on mobile A/C you are violating another law.
I am involved with conversion on larger industrial refrigeration equipment (200-10,000 HP). The cost often exceeds the cost of a new system. However, these large systems often have buildings built around them and cannot be easily replaced or the equipment is no longer manufactered so repair is the only option.
