How to Convert an R12 to the R134a System

by Dustin Thornton

Before 1995 most vehicles came with R12 refrigerant in the air-conditioning system. If your air conditioning is no longer cooling as well as it once did, then chances are you need to recharge the refrigerant in the system. Recharging an automobile air-conditioning system is rather simple, however, R12 refrigerant is difficult and expensive--you must be a licensed professional to buy it. Instead you can convert an R12 system to an R134a system with a few parts and some basic tools.

Step 1

Discard any R12 refrigerant still in the system by taking your vehicle to a licensed air-conditioning professional. Releasing R12 directly into the environment is dangerous and punishable by law.

Step 2

Open the engine compartment of your vehicle. Find the high and low side service ports for the R12 air-conditioning system. Push the low side retrofit R134a fitting over the old fitting and use a wrench to tighten it. Torque the fitting to 20 foot-pounds.

Step 3

Push the high side retrofit R134a fitting over the old fitting and use a wrench to tighten it. Torque the fitting to 20 foot-pounds. Place a retrofit label, showing that you have retrofitted the vehicle for R134a, in an obvious visible spot in your engine compartment.

Step 4

Ensure that all the valves on your manifold gauges are closed and connect the blue hose to the low side port and the red hose to the high side port. Hook the yellow hose up to a vacuum pump. Start the vacuum pump and open both the high and low valves on the manifold gauges. Allow the pump to run for a minimum of one hour. Close all three valves on the manifold gauges and switch the vacuum pump off.

Step 5

Connect a can of R134a lubricant to the yellow hose, open the low side valve and allow the vacuum in the system to draw the oil in. Inspect your vehicle's service manual for specific requirement on how much oil to add to the air -onditioning system. Skip this step if the refrigerant you are adding contains oil.

Step 6

Look up the specifics for how much R12 refrigerant the vehicle requires to work at optimum efficiency; you will be adding 10 percent less R134a refrigerant. Note that underfilling the system can damage the compressor and overfilling the system can cause the seals to leak. Close all valves on the manifold gauges and remove them.

Step 7

Screw the T-valve the top of a can of R134a refrigerant. Start the engine and switch the air conditioning to highest setting. Put a thermometer in the center vent to measure the temperature as you add refrigerant.

Step 8

Connect the T-valve hose to the low side service port. Open the valve and allow the system to draw the refrigerant out of the can--you can feel the can get colder and lighter. Allow it to drain for five minutes and then check the temperature of the inside air.

Step 9

Continue adding refrigerant until you have added 10 percent less than the maximum system capacity. Check the temperature of the inside air periodically to ensure that the system is holding the charge and that there are no leaks. Disconnect the T-valve hose from the low pressure side when you are finished.

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