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 refrigerant 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 refrigerant, but that it wouldn't do me much good if I had a leak.

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

8 Answers 8


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.

  • 1
    That is very sad :( Mar 21, 2012 at 18:44
  • Yeah, I've given up on A/C on my cars. I've gone ahead and removed it from both of them now. Luckily the climate I live in only has me seriously suffering a couple days each Summer. Mar 21, 2012 at 19:32
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    Definitely not the case for me. So if I go ahead and get the freon put in, I suppose there's no way of knowing how long it'll last before it goes again? Depends on the size of the hypothetical leak, right? Also, say there's no actual leak but the compressor or condenser or some component is flat out not working. would a mechanic be able to tell this by inspection? Mar 21, 2012 at 19:57
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    A mechanic with the appropriate tools can test the system to find the leak(s), then make recommendations on repair. Mar 21, 2012 at 20:20
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    @Aerovistae, if you have the refrigerant put in at an automotive a/c place, tell them that you appear to have a leak so they can add some UV dye to the refrigerant. You then get to drive around for a few weeks, using the a/c and take it back. The leak(s) will show up under a UV light. Mar 21, 2012 at 21:07

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.

  • 1
    Vacuum doesn't harm a system that's designed to keep high pressure in? Things won't collapse?
    – endolith
    Aug 5, 2014 at 21:38
  • Some vehicles have refrigerant pressure sensors which you can backprobe with a multimeter to see what the pressure is together with a lookup table. May 21, 2017 at 8:37

A few corrections.

(1) moisture in the system does NOT cause the suction line to frost up on the outside. Quite the opposite. Moisture in the system will freeze at the orifice tube or Tx valve and block the flow of refrigerant. No refrigerant flow, no cooling. But that will let the ice inside the orifice/valve melt, and it will cool again, then freeze again, and repeat forever.

(2) evap cores are actually more common failures since going to the higher pressure R134a instead of R12. The most common failures I have seen are (a) condenser where a rock or road FOD knocks a hole/crack in the condenser; (b) O-ring failure and most any point and (c) compressor failure. All of the non-compressor parts don't move, so the seals inside there are stressed more and fail more frequently.

(3) some vehicles have what is commonly a receiver/dryer that is on the low pressure side. If the R134a connection is on the evap side of that, you can allow liquid refrigerant in (can upside down) with no problem as that is what the accumulator is for, to prevent liquid refrigerant from reaching the compressor. If you are not sure, always keep the can upright if you are running the compressor to introduce refrigerant.

You can get a good A/C repair book at most auto parts stores. They give details about proper suction and high-pressure line pressures. But by far the best choice is to have the refrigerant reclaimed, then evacuate with a good vacuum pump for at least 30 minutes to boil off all moisture, then fill with specified amount. No guesswork.

Note that newer cars use much less freon. I drive a Toyota Tacoma that requires 22oz, just under two 12 oz cans. My wife's previous Honda was something like 16oz. If you overfill you can quickly buy a compressor, as they do NOT like liquid in the suction line, it won't compress, and something has to give. At idle, you might feel a very rough idle and squealing belt. If you turn it on while on the highway, you will likely hear a rattle of death at the very least...


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.


I'm assuming your system is R-134a rather than R-12 if someone offered to refill it for $85. In this case, you can pick up a can of R-134a at discount stores for $10 or sometimes even $8 and do it yourself. Since the system has a leak, try one of the ones with leak sealant added. This is not a good fix, but since getting AC components repaired/replaced is prohibitively expensive, it's probably your only good chance for getting working, affordable AC.

By the way, if the system actually is R-12, you can get cheap R-12 from Hong Kong on eBay. Downside is that shipping is usually by sea and takes several months. Otherwise it's basically impossible to get the stuff in the US and most developed countries.


Leaks can take place from the compressor, condenser, evaporator, hoses and dryer. I got a reconditioned compressor for my Suzuki Swift for $100 and it worked fine for a year before going bust.

Check the hose and the compressor oil seal. Changing an oil seal shouldn't cost more than $80. Easy solution, I refill refrigerant R134a every 4 months for $25. If, however, you are in Chicago or the mid east and have leakage like I do, then changing the compressor, evaporator, dryer, condenser, labor and refrigerant will set you back by $3000. It's EXPENSIVE. But in most hot regions of the US, it's the single most important equipment for survival, ahead of the power steering, auto transmission, power this and that. A car AC is not a luxury.


Freon is Dupont's trade name for R12 and requires a license to purchase and R134a is Suva. R134a is NOT Freon! Cheapest route is have a professional perform a leak test to determine where it's leaking. It may be as little as a $2 seal leaking and you just pay to have it replaced, the whole system vacuumed down and new refrigerant.


Freon fill kits are cheap enough at a NY auto parts store. I would only add freon if there is some still in the system. Even a few ounces of pressure. My experience is usually;

  • loose fittings

  • a Schrader valve where you add or check freon pressure

Rarely is it;

  • a compressor shaft seal, but they do wear out after thousands of miles.

  • very rarely a condenser coil (in front of radiator)

  • even rarer an evaporator (inside car air flow).

You can rent a vac pump I am told and usually borrow tools from auto zone for a depostit.

It's not rocket science but is engineering.

Google it and soon you will have it fixed at a fraction of the cost. Never add liquid freon as it will shatter valves in compressor.

Warm can slightly NO FLAME.... And add liquid with system off. Then add gaseous only while running.

You may have to bypass the low pressure cutout to get it to come on. Return gas to compressor cools the compressor. Rule of thumb is when suction line to compressor sweats, your gauge has enough gas. Monitor air out of duct windows open on high so cooling inside car doesn't give false cooling temp. Air should cool down as suction line getss cooler. If temp starts to inch up, you are adding too much gas.

Some newer cars are tricky as they have low speed economize features that reduce pressure on compressor near idle. This Largely stemmed from gm 1976 on up cars blowing pressure lines at idle for too long. If the suction line frost up or freezes on a warm day you h as ve air or moisture in system and need to change receiver drier and vac system before filling. All cars have a lable on how much freon a specific system holds and an empty system can be filled by that amount.

My truck takes 2 pounds 4 ounces. So that's 36 ounces or almost three 12 ounce cans. See suction line or temp output. Do not overfill.

  • You may want to edit your post to identify the actual type of refrigerant used. You cannot easily buy "Freon" at the store anymore (R-12) as the government has deemed the manufacture to be illegal. You can, however, purchase R-134a fairly easily and cheaply ... Maybe this is what you meant? Apr 19, 2015 at 2:58

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