Do-it-yourself car AC refrigerant kits are readily available, but are these DIY options a god choice? Although generally safe to use, they can be a stop-gap measure that prevents you from noticing – and repairing – a larger problem with your AC system. Before you opt for the kit, you need some basic understanding of the role of refrigerant in your AC and how to know if it's the cause of the rising heat.

Refrigerant Basics

Your car's AC contains refrigerant in a closed system. Although refrigerant is often called Freon, it can be one of several different chemicals. The refrigerant travels through the AC coils, so when air blows over them, cold air is produced.

Since your AC is a closed system, the refrigerant never needs to be topped off. Recharging, the common term for replacing the refrigerant, is also a misnomer. The refrigerant isn't recharged – instead the AC system is drained completely so leaks can be repaired before new refrigerant is added. Sometimes recharging also means just adding more refrigerant without repairing the leak. If your AC doesn't leak, it can blow cool air for decades without the need for any new refrigerant.

What Is the Right Repair?

Before you even consider a refrigerant repair, you need to make sure that low refrigerant is the problem. Often, you won't notice leaking fluids beneath the car. This is because refrigerant leaks are often slow, or they occur while you are driving, so they don't leave behind the tell-tale puddle.

The most obvious sign of low refrigerant is an AC that performs perfectly except it won't blow cold air. The fan comes on, air flow is high, and there are no odd noises – the air is just warm or hot. You may also notice it in winter if your defrost isn't working properly. If the leak is slow so the levels are only getting low, the air may be cool, but it may take longer to cool or may not cool as much as it did previously.

Recharging Basics

Keep in mind that a DIY kit is only a stop-gap repair. Your AC will still have a leak. These kits work by attaching their hose to the low pressure service port on the AC compressor. You start your car, turn the AC to high, and then empty the can of refrigerant into the port. The kits usually have a temperature or pressure gauge so you know when to stop filling the AC.

Eventually, this refrigerant will leak out. This is because your refrigerant is low only because there is a leak in a hose or connector. You can use a DIY kit as a short-term fix until you can take your car in for a proper AC repair by a professional like Modern Auto Air, but don't depend on the kits as a long-term solution.