My a/c has worked pretty well since my frame replacement, but recently I noticed it was getting a little less cool, do I bought a can of 134 to recharge it. I also figured since it clearly has a leak somewhere, and it must be a very small leak since it's worked so well for so long, that I'd look for a way to seal it. I found this on amazon:
and it sounded good, seemed like most people are happy with it. I was a little worried about the installation since it sounded a little complicated, but it is actually very simple, at least in my case. The instructions are written as if you have an empty or mostly empty system, or a system the has clear leaks. In my case I skipped the evacuating and vacuuming of the system and went right to step 11. Basically you just hook the can of sealant to your system without it running, turn your truck and ac on, and wait for the can to empty. Then you have to let it run for at least 20 minutes and that's it. I'll report back in a while to see if it actually worked, but for $28 it's a bargain.