Differences between R12 and R134a refrigerants, how their service ports differ and why the correct oil quantity matters when replacing a compressor.
MSG Equipment points out that recharging a car air conditioner is a step-by-step process and that skipping steps shortens the system’s life. The best times to recharge are the start and end of summer, while winter is a good time for diagnostics and maintenance.
The article describes the early-1990s transition from R12 to R134a. R134a requires synthetic oil, and using the wrong refrigerant can starve the compressor of lubrication — which is why the two systems have service ports of different size and design.
When a compressor is replaced, the oil quantity and type in the new unit must be checked and, if necessary, drained and refilled correctly.