Rick's Free Auto Repair Advice

Car air conditioner recharge

Car air conditioner recharge, how to do it yourself

If you follow the instructions carefully, you can perform a car air conditioner recharge yourself.

If your AC is low on refrigerant, it’s because of a leak

There are leaks and then there are LEAKS. Some vehicles lose a few ounces of refrigerant in the winter due to cold weather contraction at the connections. That’s considered a small leak, and those systems can sometimes be refilled with a DIY AC recharge kit.

Large leaks are usually caused by corrosion at the condenser or evaporator, a leaking AC compressor shaft seal or a significant leak at a connector. In those cases, the parts must be replaced or the recharged refrigerant will just leak out.

The first thing you have to understand about an AC leak

Any time an AC system is low on refrigerant due to a leak, it means that air and moisture have entered the system. Air in the system will prevent the AC from operating at full efficiency. Moisture in the system will mix with the refrigerant and oil to form acid and sludge which will eventually destroy the metering valve (orifice tube or expansion valve) and the compressor.

The correct way to recharge a leaking AC system is to evacuate the refrigerant, fix the leak, pull a vacuum to remove all water from the system and then recharge by weight.

If you just recharge using a DIY kit, without evacuating the system and fixing the leak, you will never get optimal performance and you will cause long term damage to the system!

If you intent to recharge your system and ignore the above advice, here’s how to do it.

What AC recharge kit to buy

Avoid kits with stop leak additives

Many AC recharge kits come with a stop leak additive. Be aware that those additives only work on pinhole leaks in metal components. They will not stop a leak in a compressor shaft seal, nor with they seal a connection with a rubber O-ring. Those are the most common leak locations.

If your DIY AC recharge repair doesn’t work and you then take your vehicle to a shop, be aware that stop leak products damage their expensive equipment, so you will be charged an extra fee to remove the refrigerant from your vehicle.

So purchase a recharge kit that doesn’t have any stop leak additives.

Connect the AC hose to the low pressure connector

If you can’t find the low pressure port, consult the kit manufacturer’s website for its location. Then unscrew the safety cap and connect the hose.

• Start the engine and set the AC to MAX
• Refer to the kit instructions to read the low side pressure gauge
• Add refrigerant until the pressure reaches the specified amount

Avoid overcharging your AC

More is NOT better. The under/over charge tolerance on an R-134a system is just 2-oz. If you overcharge the system, you’ll reduce cooling! The vast majority of DIY’ers add too much refrigerant.

Tips to adding just the right amount of refrigerant

• Start by buying a probe thermometer. Many pro auto parts and restaurant supply houses stores sell them.

• Roll up the windows and turn the A/C on maximum, Blower on maximum speed and recycle setting.

• Insert the thermometer into the center vents on your dash and let the A/C run until the thermometer stops moving down.

• Then start adding refrigerant SLOWLY. If you have a small postal scale, use that to measure how much you’re adding. Try to add only 2 ounces at a time. Keep checking the thermometer.

• On a 90° day, the absolute best you can hope for is a 41° discharge temp from the dash vents. If you can get yours down in the 50° range you’ll be doing well. If adding additional refrigerant doesn’t lower the temp, STOP adding refrigerant! More is not better!

WARNING: If your vehicle takes more than half a can of refrigerant, your AC system has a significant leak and the refrigerant you add will just leak out again. Worse than that however, the air and moisture in the system will form acids and sludge, causing far more damage down the road. Don’t kid yourself into thinking you’ve fixed your AC by adding a half can or more. You’re just making it worse!

If you’ve added a half can and your AC still isn’t cooling properly, STOP! Get it to a shop and have them locate and fix the leak and evacuate the air and moisture from the system.

© 2012 Rick Muscoplat

Posted on by Rick Muscoplat

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