How do you detect and deal with a freon leak?

Question

My heat works great, but my AC is nonexistent. Just blows out normal air, which in this weather is quite hot and unpleasant.

I had the freon refilled two years ago, but I haven't used the car in over a year so I don't know when the AC stopped working. It was working up until the last time I used it, anyway.

I was told it would be about $85 to refill the freon, but that it wouldn't do me much good if I had a leak.

How long should a freon refill last, and how do I know if I have a leak, and if I do, what must be done to repair it?

Answer 1

Should last forever, as long as the A/C system stays sealed (which it's supposed to be). Problem is that A/C parts are quite readily damaged and leaks are very common. Solution is to find the leaks and fix them. Usually ends up being the condensor, and it's normally recommended to replace the dryer whenever the system is touched. Those 2 alone can cost $500-1000 depending on the car. Used parts are not typically available (and if they are, they're usually not reliable anyways 'cause A/C parts are so easily damaged). Another common leak point is the compressor itself, which is equally expensive in most cases.

Answer 2

The usual leak location protocol involves filling the system and trying to determine where it's coming out, either with an electronic detector wand or with a UV light (which requires putting dye in with the refrigerant). You can get a can of refrigerant (R134a anyway, you need a license to buy R12) and a UV light at a parts store and look for the leak yourself. I've done this to see what I'm in for in terms of a repair bill. A leaking hose in the engine bay might be an easy fix, but no sign of a leak under the hood can be a bad sign, it makes me wonder if the evaporator under the dash is leaking...lots of labor just getting to the part, there.

Before adding any R134a, make sure the system is actually low first (get a can with a gauge). Note that the pressure reading is only accurate when the compressor is running. If the compressor is fast cycling (switching on and off rapidly), the system is probably low, and the compressor is shutting off to protect itself. It should start running longer if you add some R134a.

You can test for the presence of a leak without expending any R134a by sucking the system down to a vacuum. That won't tell you were the leak is (unless it's huge and you can hear the air getting back into the system), but it will tell you if you have one, and it will also give you an idea of the size of the leak (by how fast the vacuum is lost). Doing this yourself requires a vacuum pump, a shop should probably do this before adding refrigerant to a suspect system.

Answer 3

As others have said, your A/C system is sealed, and freon should never leak. We have a Jeep Grand Cherokee which had a leak in the evaporator, which is in the heater box, behind the dash.

The symptom that I saw was that I'd recharge the system with a can of R134A, and two days later, the system wouldn't blow cold anymore. Turns out evaporator leaks are VERY common in Jeep Grand Cherokee's.

I had to disassemble the dash, remove the heater box, tear it apart, replace the evaporator, reassemble the box and reinstall it behind the dash, and put the dash back together before I could recharge.

Recharging involves VACUUMING OUT the system (you attach a vaccum pump; you don't want ANY type of gas in there other than 134A), then allow the system to fill to the manufacturer's recommended pressures. I needed to go out to Harbor Freight and pick up an r134A guage set, and rented a vacuum pump from AutoZone.