You can try to spray soapy water on the lines when the ac is running. They also have uv die you can trace leaks with.

Mine was leaking from the high side line from the condenser to compressor. It was a small hole, but leaked out pretty fast.

A lot of the O rings are probably cracked from age, so they wouldn't be a bad thing to replace also.

 

There are a lot of possibilities, but compressor seals are probably the most common. Do you see any oil stains? The best way to locate it is with a sniffer, if you can borrow one. Otherwise, have a shop locate the leak for you. I'm sure you can get someone to do it for a few bucks, an then you can proceed with a fix.

 

I would say the compressor seals too.

 

Hi Manny. I've been professionally involved with HVAC for 36 years, am ASE certified, a member of Society of Automotive Engineers, and a contributor to several trade magazines. I was involved with field testing of various conversion techniques back when R134a was only a gleam in DuPont's eye. Just background so you know that I know what I know.
There are two kinds of leaks that are difficult to find, very small leaks and very big leaks. You have a very big leak. A sniffer will go nuts everywhere under the hood even if you set it to the lowest sensitivity. I suggest you try an old, and cheap, trick.
You don't want to be blowing off any excess R12 into the atmosphere, it's expensive if not hazardous to the ozone. You absolutely MUST change your receiver/drier after a leak of this size is repaired so what I'm going to tell you to do won't hurt anything.
Get an airgun with a rubber tip. Using compressed air, place the airgun against the high or low side fitting and pull the trigger. Even with the Schraeder valve in place you should be able to inject air into the fitting. Use a soapy solution and spray all your fittings, lines and components (condenser, compressor, the drier -they rust through at the bottom!, etc). You should see major bubbling somewhere. If not, remove panels to access the expansion valve and evap, repeat.

A few notes. First, the Schraeder valve is identical to one in a car or bicycle tire so it can be removed if you cannot inject air past it. They are a one way valve, they keep a gas inside, but allow it to pass from the outside to the inside.
Second, use 100 psi or so, you absolutely will not hurt anything in the system. Third, change every O-ring you remove, don't re-use them. I have tens of thousands of O-rings of every AC size ever made and can match them up for you if you can't get them locally. Use the green O-rings, not black, and you will be all set for R-134a. Green is good for either R12 or 134a.
Third, No matter what you might have heard, your hoses ARE compatible with R134a. At first we thought that wasn't the case because the R134a molecule is smaller and needed "barrier hose". But what we found is that hoses which had been used with R12 had all their 'spaces' sealed with R12 compressor oil molecules. They had been made impermeable.
Fourth, Theoretically R134a runs at higher pressures. Guess what? Not in your car, you've got an R12 compressor and it can only compress to a point. It is true that R134 operates at higher pressures, but these pressures are not hazardous to your system.
Fifth, When you convert to R134a use 85-90% of the R12 charge. So, for example, if your system uses 2.2 lbs (1KG) of R12, you will charge to a 2 lb. max. with R134a.
Sixth. Everyone knows Freon, right? No one knows that the name of R134a is Klea, but now you do.

Edit.. You still have R12??? Are you sure it isn't FR-12? I sold the last pound of R12 East of the Mississippi ten years ago. I was getting $60 a pound the last year, or $900 a 30 lb. cylinder. There was a lot of Chinese product around but I wouldn't touch it, much of it was contaminated or counterfeit or just plain dangerous stuff like Propane.

 

You absolutely MUST change your receiver/drier after a leak of this size is repaired so what I'm going to tell you to do won't hurt anything.

Hi there, would you mind elaborating on this please?

I ask because I recently had my A/C system repaired. The refrigerant had all leaked out because of a tear in a hose. Instead of replacing the hose, which would have been very costly, my indie mechanic sent the hose to an A/C specialist who repaired it. The system was then recharged with refrigerant and all is working well now.

However, my mechanic did not replace the receiver/dryer - in fact I specifically remember him saying that he checked it out and he decided it didn't need replacing. I was relieved because this meant the repair bill was less than I was expecting. Are you suggesting he should have replaced the receiver/dryer too?

 

Thanks a bunch guys! I really appreciate it.

BabyBenz, my A/C is flat empty, so dye and running it isn't possible yet. I will add dye to my sister's system since her's is good to go.

So lots of votes for compressor seals. That's upsetting. If I do replace the compressor, I'll probably flush everything out, change all the O-rings, maybe install a PF condensor and retrofit to R-134a.

DSXMachina, WOW that was an EXCELLENT post! I was getting frustrated trying to think of a way to find the leak, but your idea is fantastic! You have an impressive resume too!

Yes, I did buy some real-deal legit R-12 from a local guy. $80 for 3 14oz cans! Not bad. I have 2 cans of R-134a as well, so all I'd have to do is get an oring kit, a drier, and maybe a new compressor.

Damn. Once I get the A/C running, pulling the dash to replace the heater core will be a piece of cake!



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Thanks a bunch guys! I really appreciate it.

[snip]
Once I get the A/C running, pulling the dash to replace the heater core will be a piece of cake!


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I'm glad you mentioned that you have a vacuum pump. Not vacuuming is the biggest mistake most amateurs (meaning not doing it for a living) make. For those who don't know, vacuuming has two equally important purposes.
The first is to remove all air. Air gets in through holes and it also gets in through the sides of perfectly good hoses. Air is a "non-condensable gas" and therefore of no use to your AC system, it just displaces refrigerant.
The second purpose of vacuuming is to remove moisture, water, which got in along with the air. It does this by lowering the pressure inside the system to a point where all the water literally boils off and the vapor (steam) is sucked out by the vacuum pump. Water is deadly to AC sytems. It causes steel to rust and turns oil acidic which then eats through things like evaporators. So, air is bad, moisture is worse!

When you convert you do not have to flush out the old oil. Being incompatible with R134a it won't go into solution and it will just sit in the low spots. If you want to do a first class job, get a flush kit and flush it out of the evap, condenser and lines, but it's not required. At one time we all used special conversion oil when converting, but now we all use PAG of the appropriate viscosity (46, 100, 150). If you change the compressor the mfr. will include a note telling you which oil to use.
Be absolutely certain to rotate the compressor clutch assembly ten times after you install the compressor but before attaching the belt. This will clear the compressor of oil and prevent the BRRRAAAPPPPP noise which means you are going to have to buy yet another compressor. Something about oil not being compressible...:crybaby2: