best approach for CAC refrigerant leak

The only thing that belongs in there is refrigerant and refrigeration oil.

Leak Seals do as much damage as good. It's a 50 / 50 shot at best.

How have they been leak checking? How long does it take between topping it off?

@lbeachmike , we really aren't supposed to talk about money like that. You can edit your post by touching the "…" icon in the upper right of your posts.

start with dish soap and water at all the connections, look for bubbles that get bigger or a stream of bubbles. i think you'll sea a stream/growing foam in your case

Your contractors willingness to resort to putting leak sealer in the system should taken as a major red flag and not knowing best practices for locating the leak is strike two.

I'm glad they didn't jump to the sales pitch routine, give them one more chance and after strike three they're out! Get another opinion.

Some coil leaks are field repairable too...

An electronic leak detector is just a device with a probe on it that sniffs the air and beeps and lights some lights in varying intensity if it detects refrigerant. it gets you to the general area then especially for a leak your size soap bubbles and looking for oil will find the exact leak.

Also note if someone didn't tighten the caps on the service valves and the access valves that it will slowly leak through those.

We usually leave it up to the client, depending on the situation.

The leak seal can be a big expense without guaranteed results. We use a seal that also has a dye, so if the seal doesn't seal, then the leak should be visible with IR. Most of our clientele also have refrigerant lines that are 80% inaccessible without major demo or digging. So not all leaks are addressed equally.

Sectioning and nitro testing will leave you without AC until the leak(s) are located and repaired. It's at least 2 visits. One for the recovery, sectioning, and nitro charge. Second visit to see where the pressure dropped.

Now let's say the leak is found, and it's in the condenser coil. That's not a repair. That's a coil replacement at minimum. Now you're waiting for a new coil. For how long? IDK. Your condenser is 12 years old, not 10, and out of warranty. So now do you go through the expense of a new condenser coil now (plus refrigerant) and hope the compressor doesn't take a poop in August, or do you replace the whole condenser? Or roll the dice and do the seal? Isn't being a homeowner fun?

The compressor is unlikely to fail unless you do something extreme to it. Another leak is a possibility.

Someone who is doing refrigeration service should have the tool to replace the valve cores without losing the charge. Worst case they could pump it down(close the liquid service valve then run the condenser to pump all the refrigerant in to the condenser), replace the core, then re-evacuate the system, but the tool to replace the core without losing the charge is a standard service tool.

If the high side hose is removed with the system running sometimes the pressure can keep the schrader valve from closing. Liquid refrigerant in the high side hose of the manifold set can be mistaken for a sticking schrader as well.

The access valves(the schrader valves that the manifold gauge set connects to), should have metal caps with a metal to metal flare seal that goes over them and is wrench tightened to make the long term seal. There should be similar caps over the service valves (the valves used to trap the refrigerant in the condenser or to allow it to circulate in the system). Without the metal to metal seal the refrigerant will slowly escape.

If it is cycling there is at least enough refrigerant in the system to close the low pressure switch until the compressor starts trying to make it a solid column of liquid through the condenser and in to the evaporator so it will be leaking some but not as fast as if you added nitrogen to to increase the pressure or if it had a full charge. It should be possible to find the general area of the leak at least without adding anything to the system.