Air conditioning and refrigeration always operate on the same principle: condensation and evaporation of a liquid, which provides cooling through the removal of heat as it evaporates. You can also think of it as a gas being compressed into a liquid state, then boiling off as it returns to a vapor. In other words, refrigerant runs through a compression cycle until it's turned into a liquid, and then is routed to an evaporator where it returns to gas again and provides cooling.
If you've got a pre-1995 vehicle, here's an overview of what you'd need to do to convert your A/C to R-134a. Your experience may vary somewhat, depending on your year/make/model, and this guide should be used as an overview of typical steps.
This is a good project for new DIYers
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Take the vehicle to a repair shop licensed for A/C work that can evacuate the system of R-12 and recover it properly.
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Using an A/C flush kit, flush the evaporator and condenser to remove any remaining mineral oil in the system.
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Empty oil from the compressor and flush oil from high-pressure and suction lines.
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Add the proper Ester or PAG oil to the condenser, compressor and evaporator if necessary. Ester oil is often recommended for use with retrofit systems because it can mix with any remaining traces of mineral oil or R-12 and still lubricate the system properly.
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Install the retrofit adaptors on the high- and low-side air conditioning ports. Use a wrench to tighten them.
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Using a vacuum pump and gauge, pull a vacuum in the system for a minimum of 45 minutes to confirm there are no leaks. If the system does not hold a vacuum, you'll need to fix any leaks before moving to the next step.
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Screw the T-valve to a can of R-134a, start the engine and turn the A/C to its highest setting.
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Connect the T-valve hose to the low side service port. Open the valve and let the system draw refrigerant out of the can, monitoring the temperature with a thermometer in the center vent. You'll be able to feel the can getting lighter and colder as it empties.
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Continue charging the system until it's at 10 percent less than full capacity. Close the valve and disconnect the T-valve hose and can when the system is charged.
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Place the retrofit label under the hood indicating the system has been retrofitted to prevent contamination with R-12 during any future repairs.
Check what kind of compressor your system is equipped with. R134a increases discharge pressure, and some older compressors are not up to the task.
Don't overtighten the adaptors. If you're unsure, use a torque wrench set to around 20 lb-ft.
In the earliest days of air conditioning, engineers experimented with propane and ammonia as refrigerants, but those had obvious drawbacks; one is very flammable and the other very toxic. What was needed was something that was neither and was safe to handle, and in the early 30s GM's chief engineer Charles Kettering developed dichlorodifluoromethane, also known as R-12. At the time, Frigidaire was a wholly-owned subsidiary of GM, and Kettering's team also took the lead on developing R-12 refrigerant.
By the '60s and '70s, automotive air conditioning was quickly going from being a luxury to a must-have option, especially on many full-size and luxury cars. R-12 was the standard refrigerant for automotive A/C systems for many, many years. It was good for its designed purpose; R-12 was a very effective refrigerant and was even used as a propellant in aerosols for years. That was all about to change, though.
Beginning in the '70s, research began pointing to R-12 as being an ozone-depleting greenhouse gas. Indeed, the numbers pointed to R-12 as being responsible for about 50 percent of a vehicle's total global warming potential (including fuel over the car's life cycle). Starting in the early '80s, engineers were looking for an effective replacement for R-12 and ended up with R-134a.
Refrigerant technology continues to advance and improve with the need to protect the environment. But for now, sit back and enjoy that nice cool ride.
Are you looking to make this conversion? Let us know in the comments.
