If your cars’ AC system is low on Freon (It’s not really Freon, it’s a product called R-134a), you have a leak. No two ways about it. Your cars’ AC is a closed system, meaning that it circulates the same refrigerant over and over again and as long as there’s no leak it will never run out. Now, having said that, some leaks are big enough that they need immediate repair if you want your system to work, and some are very small, so small that you don’t have to re-charge the system but every other year or so.
So where do these leaks most commonly occur? Far and away the most common place for a leak in the AC is at the service ports. There are two of them, one at the high pressure side and one at the, wait for it…low pressure side (Who woulda guessed?). Inside the service ports are little valves that look all the world like the valves in your bicycle tires. Over time the seals that keep them from leaking wear out or get hard and they fail. Easy enough to replace when you have AC service done and we typically replace them as a preventative measure when we re-charge a system.
Now, the AC system in your car has a number of rubber o-ring seals in it as well and these are the second most common spot for leaks to appear. Of those we see more leaks at the AC compressor where the hoses attach than just about anywhere else. After that it would be the o-rings that seal the system to the thermal expansion valve next to the firewall. The best repair for failing o-ring seals is to replace them all. After all, if one’s gone, the rest will be following soon. Bunch o’ quitters!
You’ve probably notice that there are a couple of rubber hoses associated with your cars’ AC too. Those rubber hoses are the third most common point of failure as far as leaks go, usually at the metal collars that attach the fittings to the hoses. You’re pretty safe just replacing the offending item, re-charging the system and going on your merry way.
The last items are way less common: A leaky compressor. The compressor has a seal on the front behind the pulley/clutch that’ll go bad occasionally. Also the compressor splits in half around the middle and there’s a seal that will leak. When this happens get ready to replace the compressor ‘cause it’s really tough to get the darn thing to seal up correctly after disassembling it.
A hole in your condenser. That’s the thing at the very front of your car behind the bodywork that looks like a radiator. They get hit by rocks from time to time, something to which they react poorly.
Way down the list but something we still do see is a leaky evaporator. That’s another piece that looks a bit like a radiator. It’s tucked up way up under your dash and it’s pain to get to. You don’t want a leaky evaporator, they’re labor intensive.
I hope this helps a little.
From your Local Mechanic, All Tune and Lube Total Car Care. Complete Auto Repair and Maintenance.