One step toward converting your R-12-based air conditioning system to use R-134a refrigerant is changing the compressor oil. The mineral oil used with R-12 cannot be mixed with the oil used in R-134a, hence the need to remove it from the system to avoid damage to the compressor. Draining the R-12 oil out of the compressor lets you add R-134a oil to the system without risk of compressor failure.
Park your vehicle on a flat, level surface. Raise the front of the vehicle with a floor jack and support it with jack stands for extra clearance. Place a catch pan underneath the compressor.
Locate the high side and low side A/C lines running from the compressor. Make sure the A/C system is empty and unpressurized before disconnecting the lines. Use a quick disconnect tool to disconnect the lines and direct the lines into the catch pan.
Locate the drain plug on the compressor if equipped. Remove the drain plug and let the oil drain out of the compressor for at least 15 minutes. Turn the compressor by hand a few times to dislodge oil from the inner chambers of the compressor.
Reinsert the drain plug and reconnect the high side and low side A/C lines when finished. Move the drain pan out of the way. Remove the jack stands and lower the vehicle to the ground. Dispose of the compressor oil at the nearest automotive parts outlet or repair shop.
