Vintage Mustang Tech Questions and Answers
Beyond the Basics
Chill Out, Man!
I am at wits end trying to eliminate leaks at all the connections in my A/C system. I have bought a new aluminum York-style compressor, a condenser, a dryer, and hoses via the aftermarket. These are all the original style with compression fittings similar to that used in R-12 systems. I want to convert to using R-134a with this same system without significant additional expense (if possible). The underdash evaporator has been tested and is not leaking. We cannot seal these connections to save our lives. Is there a gasket material or sealant that I can use to seal up these leaking connectors? Any other advice? Thanks for your time.
Via the Internet
I totally understand your frustration. Even with OEM suppliers, sometimes the fittings just don’t want to work together. Murphy’s Law dictates that we will be the one to get the bad part! There are two types of fittings on the original-style system: O-ring and flare. Some of the flare fittings were single, and some of them were double. This might be one of the reasons you have a leak, but let’s start at the beginning to solving this problem.
First off, go ahead and convert to R-134a. Finding a leak is much, MUCH cheaper using R-134a than it is with R-12! The first thing you need to do is find where the leaks are, and to do that you need to go ahead and do a dye check on the system. You don’t have to fill it up all the way—just enough to get the compressor to kick in. Half should be enough to get it to turn. Run the dye and get your UV light out and find where the leaks are, and then go from there. You may luck out and find a wet connection, or you can use soapy water and allow the leak to make bubbles, but identify all the leaks first.
If the leak is an O-ring fitting, it might be that you tightened them too much when you installed them. Not lubricating the O-rings (kits usually come with the proper ester oil) and tightening them down too much can pull or push the ring out of place and cause a leak. It won’t hurt to go through and replace the O-rings—even if they are new. Sometimes with aftermarket parts the specifications aren’t quite tight enough, and you have to massage the O-rings to compensate. Some A/C sealants act to swell the O-rings, and running the stop-leak in the refrigerant causes the O-rings to swell slightly. If it is a flare fitting, get back with me on which one it is and let’s research if it should be a single or double flare. I think some of the fittings were double flared, and if your aftermarket lines are single, that may be the cause (just like brake lines). If you can’t get rid of the leak by cranking on the flare fitting, it will then be time to get the manufacturer to exchange the ill-fitting line. It’s a frustrating thing to track down all the leaks, but start with the dye and take them on one at a time.
Photography by Dave Stribling