Dear Members,

I live in southwest area of Houston and trying to fix my new '64 Coupe with factory AC. Apparently I must have a very small leak(s) in my system as when I put a vacuum on it, my gauges' needle don't move at all over night. And when I filled it up with R12 few cans, the system would go back to blow warm air after few days. Another member recommended me to try dry nitrogen on system. I checked videos and I think I would follow same steps like refill freon but bring pressure up to like 150 lbs on both low and high gauges. However, I searched on internet and I think the only place I can get a small dry nitrogen tank is at Airgas store by 610 of Houston. Has anyone in Houston found a place that would let me either rent a tank or buy a small tank to do this work? Appreciate any other advices on this. Thank you in advance.

 

Understand, that a leak may not expose itself under vacuum but it could still leak under pressure

 

Buy yourself a good refrigerant leak detector. It should/will find your leak. Your leak could be in the evaporator coil, and nothing but a leak detector will find it. I can advise how to test with it. My own leak detector was a Inficon TEK-MATE, and it performed very very well. But you can buy one for less $$ if you want.
Dry nitrogen is what you want/desire for purging your system and the initial leak checks before filling with refrigerant. But most of us can maintain and repair the older AC systems without ever using dry bottle nitrogen. But it is sure very nice to have. If you really want it, rent or buy a small tank (and buy a regulator) from a bottled gas company in your area. There are many.

To keep your old AC system running and performing, you either need a lot of $$$ and a very good HVAC friend, OR decide to do the work yourself and get the tools and the training/advice. There is no other good/alternative option.

FWIW.

Larry

EDIT: In Houston, find a welding supply shop or a HVAC supply shop in your area. Use Google to find. They rent bottled welding gases, and also bottled dry nitrogen. Every HVAC tech has one in his truck, and Houston must have 10,000 HVAC trucks running around the city. So, easy to find where they buy their supplies.

 

If you go to an A/C specialist, they will put a dye in the system that will show you where the leak is.

 

I have injected dye in the system and didn't see any leaks with special flashlight and yellow glasses. I did this first before I did the vacuum pump step.

 

Agree....................and you can also do this job yourself if you buy a gage set and the dye. But over the years, I have found that the refrigerant leak detector is a much better solution. Also less messy.

If leak is in the evaporator coil, you will need to check for it in the AC condensate that drains under the car. The leak detector can detect from checking just the cabin vents. Leak detector is also better at diagnosing a compressor seal leak (in my opinion). I am not a fan of the UV leak detectors, but they can be useful in some circumstances.

OP needs some help one way or the other. He just needs to decide which way he chooses to go: pay $$$ and find a good shop, or educate himself and find and fix the problems.

Larry

 

I’ve been helping a little bit through private messaging, and he’s already tried the dye and didn’t find anything. But recently he found with a leak detector a hint of a leak around the O-rings, where the manifold connect to the back of the compressor.

i’m a little out of my depth beyond basic disassembly and reassembly and charging so I’m hopeful that others in the forum with more expertise than I can be of assistance.

 

Jeff:

Don't be so humble. You are a CF Tech Contributor for your excellent AC advice and video/tutorial in the past. You are also a real NASA rocket scientist/consultant. Your advice is always appreciated.

Larry

 

To the OP: I have also found slight leaks thru the rubber AC hoses in a few cars. Sometimes you have to move them around to pickup with a leak detector. So don't discount these. I know of one guy who wrapped them in plastic garbage bags and sealed the bags and bag ends. Left them for a few days and then put a small slit in each bag and used a leak detector probe in the slit. Extreme but sometimes necessary.

Did you collect the condensate from the evaporator drain under the car and check the water/condensate for the dye?? Probably need at least 2 oz of water/condensate to have sufficient sample size. Any dye found in this condensate indicates an evaporator leak.

Larry