How to Convert From R12 to R134a
- 1). Drive your vehicle to a certified air-conditioning repair shop. Allow a qualified technician to remove all remaining R12 refrigerant from your system using a refrigerant recovery system. Federal law prohibits the release of this gas into the air.
- 2). Instruct the repair shop to flush the system to remove all traces of mineral oil. This will also remove any solid contaminates from the compressor. Mineral oil is not compatible with R134a PAG (polyalkylene glycol) oil, and mixing them could lead to compressor failure. Another option is to use ester oil, which is compatible with both R12 and R134a refrigerants.
- 3). Return home to complete the conversion. Begin by attaching the new adapters to the old valves. There are two valves: the high-pressure valve is the larger one, and the low-pressure valve is the smaller one. The low-pressure valve is on the line that runs from the accumulator to the compressor, and the high-pressure valve is on the line from the compressor to the condenser. The adapters screw onto the existing ports on the old R12 system, and will attach only one way so you cannot screw them onto the wrong valve. Check the repair manual for a diagram if you are unsure of the location of the valves.
- 4). Inspect the valves, hoses and pressure switches for any signs of wear or excessive oil buildup. Replace any parts that leak or show excessive wear so the R134a refrigerant will not leak from the same place. R134a has much smaller molecules than R12, so a small R12 leak could be a large R134a leak.
- 5). Check your vehicle's repair manual for the exact amount of oil to add to the compressor via the low-pressure fitting to lubricate the system. Use the oil and hose included in the conversion kit.
- 6). Connect the can of R134a to the hose included in the conversion kit. Turn the T-valve directly on top of the can to puncture it, then very slowly turn it the opposite direction to release a small amount of refrigerant from the hose. This removes all air from the hose so it will not be trapped in the system.
- 7). Close the T-valve fully and connect the other end of the hose to the low-pressure valve on the line from the accumulator to the compressor. The hose will fit only the low-pressure valve.
- 8). Turn on the vehicle and run the air conditioner at the coldest setting. Hold the can of refrigerant upright and open the T-valve to allow the refrigerant to go into the air-conditioning system. The compressor may not turn on instantly. There is a cutoff switch to prevent damage from low system pressure. Once enough refrigerant fills the system, the compressor will engage.
- 9). Watch the gauge on the hose connected to the can of R134a to add the appropriate amount of refrigerant to the system. Overfilling or underfilling may affect the system's cooling ability. Once the system is full, turn the T-valve completely off and remove the other end from the low-pressure fitting.
- 10
Place the plastic caps on the low- and high-pressure fittings and apply the retrofit R134a label in a prominent place to indicate that the vehicle uses R134a refrigerant. The caps and label are included in the conversion kit.
Source...