Overcharged car AC system: How to remove excess refrigerant

Learn how to remove excess refrigerant from an overcharged car AC system safely

An overcharged car AC system can lead to poor performance and potential compressor damage. Recognizing the signs and knowing how to address the issue is crucial for maintaining your vehicle’s comfort and efficiency. Contrary to popular belief, more is not better when it comes to maintaining the correct refrigerant charge in your car’s AC. The opposite is true. R-134a refrigerant, for example, has just a 2-oz window; if you overcharge by more than 2 ounces, you will decrease cooling, not improve it.

Symptoms of an Overcharged AC System:

• Warm air— An overcharged car AC system can’t cool the air.
• Unusual noises— Overcharging can cause the AC compressor to lock up, causing the drive belt to squeal or chirp. It can also cause the compressor clutch to slip and screech. An overcharge can permanently damage the AC compressor. Inside the cabin, you might hear hissing or knocking sounds.
• High-pressure readings— If you have a pressure gauge, you’ll notice abnormally high readings on the high-pressure side.
• Compressor cycling— The compressor may rapidly turn on and off or fail to engage at all.

Venting refrigerant into the atmosphere is illegal, so you must recover and recycle it.

R-134a is considered a greenhouse gas and can’t be vented into the air. So you’ll have to capture the excess refrigerant in a refrigerant recovery bag or recovery tank and then take the recovered refrigerant to a shop to be recycled.

To remove refrigerant, you’ll need a manifold gauge set. However, refrigerant recovery bags can cost upwards of $75 to $112 and a recovery tank is closer to $100, so overcharging can turn out to be a costly mistake. Find a recovery bag at any appliance parts store or here.

Recover the excess refrigerant with a recovery bag or tank and a manifold gauge set. Then, take it to a shop to be recycled

How to recover excess refrigerant

Close the handle valves and connect your manifold gauge set to the high and low ports on your car’s AC system. Close the yellow hose to the recovery bag or tank. Start the engine and turn on the AC. Slowly open the LOW side valve for a few seconds. The bag will begin to fill. Note the high and low pressures and compare them to the the chart below:

65°F Ambient temperature: Low side pressure 25-35 psi High side pressure 135-155 psi
70°F Ambient temperature: Low side pressure 35-40 psi High side pressure 145-160 psi
75°F Ambient temperature: Low side pressure 35-45 psi High side pressure 150-170 psi
80°F Ambient temperature: Low side pressure 40-50 psi High side pressure 175-210 psi
85°F Ambient temperature: Low side pressure 45-55 psi High side pressure 225-250 psi
90°F Ambient temperature: Low side pressure 45-55 psi High side pressure 250-270 psi
95°F Ambient temperature: Low side pressure 50.55 psi High side pressure 275.300 psi
100°F Low side pressure 50-55 psi High side pressure 315-325 psi
105°F Ambient temperature: Low side pressure 50-55 psi High side pressure 330-335 psi
110°F Ambient temperature: Low side pressure 50.55 psi High side pressure 340.345 psi

Continue releasing refrigerant into the recovery container until the high and low pressures fall into the normal pressures listed above.

Why you should never release refrigerant from the Schader valve

With the system off and equalized, the refrigerant pressure is about the same as the ambient air temperature (at 80°F ambient the refrigerant will around 86 psi).  R-134a boils at -17.34°F, so it’ll shoot out of the port fast and cold— cold enough to produce frostbite. I’ve seen reports of DIYer who vented refrigerant and it shot into their eyes, freezing their cornias. It’s dangerous and illegal. Don’t do it.

©. Rick Muscoplat