Been trying to figure out what to do with the A/C on my 71 Riviera. I think I'll just stick with R-12. It's not that expensive (relative to 5 or 10 years ago). I want to check my system for leaks first though before I charge it with the $12/can stuff. Any tips on how best to do that? I think things are in pretty decent shape because there seems to be a small charge in it already. The compressor switches on too. Just no cold air. Thanks!
Unless you have access to a sniffer, the only way to be sure it don't leak is to pull it down into a vacuum with the guages attached. If it holds vacuum for at least 30 minutes, it can be assumed to be ok. When I do it, if I have the time, I actually leave it sit overnight and check it in the morning. Sometimes it may appear that you have a slight charge in the system, but actually it may be empty. Before putting any expensive R-12 in there, you'd better make certain the system is tight first or you'll surely waste it. If it is in fact empty, a new dryer would be a very good investment. Personally, I'd skip the R-12 and just use Duracool but that's just my own biased opinion. I think it works better, it's cheaper, and it's easier to get. If it slowly leaks out, so what. I'd rather lose $30 worth of refrigerant than $150 worth all over a leak I didn't know I had. Also, some leaks won't show up until after the system has been in operation for a while. Typically, these show up next spring when you flick it on and all that comes out is warm air.
Yeah, been thinking about Duracool. Saw on the EPA website though that it's not certified, blah blah blah. Due to the flammable components apparently. Here's some info: http://www.epa.gov/ozone/snap/refrigerants/hc-12a.html But if I did use it anyway, will it blend with any R-12 that might be left in my system? Seems like I should do an evacuation of the existing system first. Any recommendation on tools for vacuum-testing an A/C system? Thanks!
I am and A/C contractor, if you know someone in the A/C business borrow their micron guage (how many microns of atmoshere in parts per million) when pulling the vacuum. They are not expensive $40.00-100.00 and make sure you can pull to at least 1000 microns. If you can hit 1000 or less microns there is no leak. If you can't pull to 1000 microns there is moisture entering the system through a leak but the guages may show 28 inches. Ignore what the guages show as they are irrelevant to how much moisture is still in the system. Only pull from one shrader valve high or low side and cap the other with a good cap. The guage can show 28 inches of vacuum and you can still have a leak. The micron guage does not lie. I normally pull to 500 microns and will guarantee there is no leak. Mikey
Thanks... unfortunately I don't know anyone with such A/C equipment. I did look around on ebay and I can get a micron gauge for around $75-$100, but then I still need a vacuum pump and the proper fittings... and it starts to get expensive enough that I might be better off just bringing it into an A/C shop for the test I guess. Anyone around Southern California that has this stuff I could use?
But if you buy the tools this time (spending the money you would save at a shop), the next job will cost you very little. Once you have the tools, you have them available for life if you take care of them. A micron gauge is a very good tool for refrigeration, but it's a bit of overkill on MVAC. It's not essential for a good job. The key is to replace any original rubber in the system. Those are the items that deteriorate with age. There is a more reliable compressor shaft seal available too, if you have an A-6.
I wish I had a micron guage............. :ball: He's right about a/c tools. Once you learn how to do it, you'll be able to fix the a/c in the daily drivers too. For what it costs to take them in, you can have all you need. And r-12 guages are dirt cheap right now, even a set of 134 guages aren't too costly, and for DIY repairs, that's all you really need is a cheap set. If you don't abuse them they work fine. NAPA has a huge selection of adapter fittings if you need one. I adapted an old refrigerator compressor that I use as an evac. pump. She pulls down to 29.5" and all I need to do is squirt a few drops of oil into her every now and then. It doubles as an awesome brake bleeder too (through a seperator jar of course so the brake fluid don't go into the compressor) :idea2:
Yeah I think I will get the tools. I realized there are simple air-powered vacuum pumps out there for pretty cheap. Thanks for the info!
Hey one more question... When I vacuum-test the system, will the vacuum pull the oil out? Or if I open the valves slowly will the oil remain? Thanks again.
I was in the HVAC field for a short time, mainly doing residential AC system installs.....standard procedure was to pressure test the system using nitrogen. If it held pressure for 30 min, we assumed it was tight. We would then evac the sys with a vacuum pump to 200 microns (???I forget exactly) and charge with refrigerant. Another method is to add a small amount of cheap refrigerant, pressurize with nitrogen, and use a 'sniffer' to detect leaks. Then there was the simple 'soap solution' test used on joints and connections.....surprisingly, it will detect small leaks! Interesting question about removing the oil....I don't knowo No:
I too am an HVACR contractor but I started with the A/C on my own car in 1985. You won't pull the oil out of your car with a vacuum pump. The micron gauge is a good tool but I feel to be sure you need to check the system under pressure as well. It's rare but I've seen leaks that only show under pressure and not under a vacuum. Your A/C system will only see pressure anyway. I like to use nitrogen to pressurize systems and use a leak detection solution to check for leaks. The solution is basically liquid soap but the manufacturer claims it works much better("Big Blue" if you want to google it). I used Palmolive years ago and it worked fine. If I really want to be sure and I have the time, I'll leave the nitrogen in overnight and check for pressure loss the next day. I also have an electronic leak detector that I rarely use due to its unreliability and the fact that it will not pinpoint a leak but only give the general area. They're better on cars than in HVACR but I still prefer the bubbles. As a side note, on my own car I rebuilt my hoses and pressure checked them. No leaks. I put all new o-rings in and pulled a vacuum. Held for hours. Pressurized the system with nitrogen and bubble tested. No leaks. Did the overnight nitrogen test. Passed. Evacuated, charged, cooling fine. Go for a test drive and five miles later I lose cooling. Some of the refrigerant leaked out. ou: This one had me stumped. It was the compressor shaft seal. It would only leak when it was running. I'm sure guys that do more cars than I would have caught this sooner but man I was freaking.
I agree! A complete vacuum is only 14 lbs below atmospheric. Compresser pressure approaches 300 lbs, so you are looking at 20x the pressure! You need to simulate operating conditions to ensure it is leak-free. BUT I can't recommend that much test pressure for an automotive system, hopefully someone with more automotive experience can comment....
The factory test pressures are in the shop manuals and should be used however I test to 400 psi in HVACR daily. I have and wouldn't hesitate to take a car up to 300 psi. At that pressure a decent sized leak will be audible. If it's going to leak I want it to leak nitrogen right then, not refrigerant later. It's funny this subject should come up. I went to a new customer today on a walk in freezer call. There was a problem with the condenser fan and someone never connected the high pressure cut out. My gauge read a little over 500 psi and climbing when I disconnected the power. The gauge only goes to 500. That's the highest I can remember seeing in 18 years in the business.
Stay away from the air powered vacuum pumps. They are not worth the money. They do not pull a good enough vacuum unless you have HUGE amounts of air available. Go to www.ackits.com and check out their DIY starter kits. 3-400 psi to pressure test a system is usually ok but it's a real acid test of the system. The pressure relief valve on older R12 systems usually opened near 400psi. Some folks will say that "my evaporator blew out at 350psi", This type of pressure testing will also show up WEAK parts in a hurry. An MVAC system should handle 400psi of test pressure, but if some of the parts are marginal, this can cause problems. The evaporator and other low side components never see 200psi in operation, even static pressure on a very hot day. Although nitrogen is certainly preferred, I often pressure test with 250psi of dry shop air BEFORE doing the repair. You don't want to use shop air with a new desiccant. This will show leaks in major components, like evap, hose, condenser, compressor body and shaft seals. Someone mentioned Big Blue. It's good stuff. A really good alternative for DIYers is kids bubble mixture, It's blended to have lots of surface tension to make bubbles. I'd say it works about as good as Big Blue.
