Rick's Free Auto Repair Advice

Learn How To Recharge Your Car’s AC yourself

Recharge your car’s AC Yourself using this Step-by-step

Follow this guide to recharge your car’s AC yourself. But understand that your auto AC is a sealed system. If you’re low on refrigerant, that means you have a leak. Any time you lose refrigerant, you also lose some AC oil. If you don’t add oil when recharging the system, your AC compressor will wear out much faster.

But worse than that, as it wears, the ground-up metallic particles will spread throughout the entire system, making it a much more costly repair when the system finally fails. You’ve been warned.

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 be topped off with a DIY AC recharge kit.

However, 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 again, and often right away.

What’s important to understand about an AC leak

Any time an AC system is low on refrigerant, it means that air and moisture have entered the system and oil has also left 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.
• Loss of oil means the compressor will wear out faster and spread metallic debris throughout the system.

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, add oil, 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 will cause long-term damage to the system!

Which AC recharge kit to buy

Avoid kits with stop-leak additives

Many AC recharge kits come with a stop-leak additive. Be warned that those additives only work on pinhole leaks in metal components. They will not stop a leak in a compressor shaft seal or seal a connection with a rubber O-ring, which are the most common leak points.

Here’s the warning about stop leak products: If your DIY AC recharge repair doesn’t work and you then take your vehicle to a shop, the shop will test the refrigerant first to make sure there’s no stop leak in the refrigerant. If they find any, they will charge an extra fee to recover and recycle. Stop leak products can damage a shops regular recovery machines.

If you plan to recharge your car’s AC yourself, shop for a recharge kit that doesn’t contain a stop leak!

Connect the kit 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/overcharge tolerance on an R-134a system is just 2-oz. If you overcharge the system, you’ll reduce cooling! The vast majority of DIYers add too much refrigerant. Please don’t make that mistake. If you’ve added refrigerant and it still doesn’t cool properly, there’s something else wrong. More refrigerant won’t fix the problem; it’ll just make it worse.

Tips to adding just the right amount of refrigerant

• Buy a dial or digital probe thermometer. Many pro auto parts

This image shows a probe dial thermometer that you place in the center duct to determine AC efficiency

AC duct thermometer

and restaurant supply houses stores sell them.
• Roll up the windows and turn the A/C on maximum, the blower on maximum speed, and the air set to the recycle setting.
• Insert the thermometer into the center vents on your dash and let the AC 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



Custom Wordpress Website created by Wizzy Wig Web Design, Minneapolis MN