62Jeff

My 65 factory A/C coupe is showing signs of a failing A/C system.

Configuration
The car is completely stock but for a POA in place of the STV.

The drier and compressor were restored by Classic Auto Air in 10/2006. Hoses were replaced in 7/2006. System was fully charged with R-12 11/2006. The compressor and associated manifold is a 1966 corvette compressor, the drier is correct 65 corvette drier.

Current Behavior
Aside from the oil that this compressor has been throwing out of the front since the day I installed it (Classic Auto Air said it'd do that for the first 8-10 hours of run time, which I've long passed), the cooling ability has been diminishing the last few times I have driven the car. This morning I drove it on some errands and the A/C almost just doesn't make a difference.

After running the car for a while with the A/C on, I came home and popped the hood. The POA valve and general area was very wet with condensation just like I'd expect. This tells me it's getting cold gases to it. The compressor was making a noise similar to the sound made by airing up a tire from a air tank, and was VERY hot. I did confirm that the air out of the A/C vent got a lot hotter if I pulled the temp ****, suggesting that the heater valve is working properly and not artificially elevating the air temps when on the coolest position.

So now what?
I don't plan to take this car to any A/C repair center. I plan to do any work I need to myself. I've got 56 lbs of R-12 left, waiting for my licensed buddy to install when ready.

Where should I start? I have an IR gun and I'm not afraid to use it to help identify problems if that would be of any value.

I know the compressor may need to go back to fix the oiling issue, but I'm curious if there are other things I should do as well - so that I don't simply get the compressor re-rebuilt and then have the same cooling issues.

I realize there's an excellent A/C forum out there, but I'm just more comfortable here for my corvette advice.

Jeff

67vetteal

Hi Jeff, As with any malfunction, Diagnosis is everything. First, do not run that system for any reason other than to find your problem. You mention a friend who is experienced. Wait for his appraisal and expertise. Second, I suspect your Freon is Low as there should be Frost showing on the lower half of the POA. Third, it is probably the Comp. that is at fault. Very warm, yes, Hot, no. If it has slung as much oil as you say be certain it has lost Freon as well. A Gauge set will confirm this. If the Comp. has trashed itself your system will need a complete flushing. You can do this yourself. I can understand your reluctance to go to a "Pro" shop seeing as in and out seems to be today's standard. DIY is a practical approach if you do your homework.
AND, the ACFORUM.COM is the place to start. Al W.

KC John

Can you see bubbles in the site glass on the drier?

62Jeff

I'll check.

Got it.

The moisture was after shutting the car off. I'll run the system and watch the POA while running to see if frost appears.

That's what I'm thinking as well. While diagnosing I'll put my IR gun on it. It was at 150 degrees about 20 minutes after shutting the car off when I thought to check it earlier today after starting this thread.

Yeah, I'll find that out when the compressor goes back to Classic Auto Air.

My expectations of people is sufficiently low that I'm rarely disappointed and sometimes pleasantly surprised. I also do not trust that I could take a 30 lb can of freon to a repair center, and get 26 lbs back plus a fully charged car. I somehow suspect they'd tell me they needed 15 or 20 lbs to diagnose the problem, which means they stole it for their own use.

62Jeff

Just pulled the car in the driveway and let it idle for 10 minutes with the A/C running.

It is 90 degrees F. outside.

POA - Cool, a little frosty, but frost doesn't build up very thick. IR gun says it's 90 degrees there but I'm probably picking up ambient heat from the near-by exhaust manifold which is right at 430 degrees on each port (at least it is burning consistently)

Drier Site Glass - As foamy as a head of poorly poured beer

Compressor - The temperature at the top of the compressor, just behind the clutch, is 189 degrees. The rear of the compressor near the manifold was low 170s. Oil continued to come out while I watched.

The air coming out of the vent was cooler than not having it on, but not what it should be. I don't have a thermometer to stick in the air vent to measure temps. Ghe IR gun never produced a good result when I tried it there several months ago.

My uneducated guess suggests basic compressor failure at the clutch seal.

Thoughts?

KC John

I can't say where the leak is, but the site glass should be clear if the freon is full. Looks like you now know why it's not blowing cold.

62Jeff

Yeah, when my buddy charged the system up I watched the site glass go from empty to foamy to clear.

Don't know why I didn't think to check that first today. I guess I assumed with my luck that it was something more complex like a stuck POA.

Stan's Customs

I agree that low freon is the cause of no cooling. (bubbles)

The leaking compressor seal is likely the cause of refrigerant loss...and perhaps the reason for any abnormal compressor noise you may have.(Being low on refrigerant oil will cause a compressor to be noisy) Be sure to add an oil charge when your friend charges the system.

Also just to be sure ...look at all the line connections. Any other seepage will be visible on the dust around the connections. It will be a little oily(unless you've washed the engine lately. When you remove the compressor or change the seal, break down the oily connections and replace o-rings or tighten if they don't have o-rings.

I'm sure your friend has an evacuator...but if he doesn't get one (rental/borrow) and pull a vacuum on the system for a few minutes to be sure it is moisture free. I would replace the dryer prior to this. It's cheap and will make a big difference if the old one is contaminated with moisture due to the leak. Be sure the system it will hold a vacuum for a few minutes once the pump is turned off. If it doesn't you still have a leak and you will just loose expensive freon before operating very long....

After that you should be good to go..

Good luck...Stan...

62Jeff

Thanks Stan. I'll check everything out as you suggest. All new O-rings were installed at the drier, condenser, and compressor manifold when I assembled the rebuilt components in Nov 2006. But there may still be leaks.

My friend does have a vacuum pump. When I put this system together in November 2006, we put the vacuum pump on it and pulled it down to 32" in very short order and then let the pump run for 4 hours to help void any moisture from the system. I then closed the gauges and shut off the pump and let the car sit overnight. The next morning the system was still at 32" so we knew at that time the system seemed to be solid and that gave us the green light to charge it up.

Oh well it's only time money and effort to do it all over again.

Powershift

Jeff:

My guess is that you are very low on refrigerant: bubbles in the drier sight glass, hot compressor, not cooling very well, oil/refrigerant leakage at the compressor seal, etc.

I would get a set of refrigeration gages and check your system pressure first thing tomorrow after everything is cool. If your pressure is less than 70 psig at 70 F or 84 psig at 80 F ambient temperature than you do not have any liquid refrigerant remaining, only gas.

If the pressure is around 70 psig, start the car and run the AC for a few minutes until the system pressures stabliize and see what your suction and discharge pressures are. Shoot for 2000 engine RPM with the inside blower on high and the windows open. Then recharge your system until the bubbles disappear from the drier sight glass and the discharge pressure comes up to around 180-200 psig. If possible weigh your refrigerant tank. A complete charge is around 3 pounds of Freon-12, so you don't want to (grossly) overcharge.

At this point the suction pressusre should be 30 psig, if the POA valve is operating correctly. An the air temperature from the vents should be around 40-45 F.

I would then keep track monthly of how things are cooling to get an idea of how much refrigerant you are losing. Back in the day, many of these systems would lose a 1/2 pound to a pound of refrigerant a year. Obviously a tight system is better, but you have plenty of Freon-12 to play with. But you don't want to waste it. The front seal may wear in with continued use. Ideally, the AC system should be run every few weeks or once/month to keep the compressor seal lubricated and reduce/eliminate leakage.

I purchased a refrigerant leak detector a year ago to help troubleshoot my system, and found a leaking o-ring. You may have a similar problem. The detectors are around $200, but are an excellent diagnostic tool for a DIYer. Especially with what Freon-12 is selling at nowadays.

The Chevrolet Chassis Service Manual also has an excellent section on troubleshooting heating and air conditioning. You should get a manual if you don't already have one.

Larry

Classic-Chevy-Guy

Jeff,

I am a pure novice at A/C and will be going thru the same process on my 64 Coupe. I was under the impression that you can add Dye to the R12 and examine the lines with an Ultraviolet light to determine where it is leaking. I purchased an LED Ultraviolet Flashlight from Harbor Freight Tools and seems to work great. Is that what you were referring to when you mentioned IR?

Best of Luck.

Ralph

62Jeff

Hi Ralph,
When I said IR, I meant an InfraRed thermometer. It's a neat point and shoot device that lets you gauge the temperature of objects. Random e-bay search pulls up this example, which is not exactly the one I have.
http://cgi.ebay.com/Non-Contact-Hand...QQcmdZViewItem

By using it I could tell the temperature of the compressor, the drier, and other A/C components. It is the first thing people reference here on the forum when someone seeks help with an overheating cooling system. We start with "Have you used an IR gun to confirm the temps are really above 180?".

I also recently used it to discover a massive air leak in the ducting inside the wall of my home when I found a patch of drywall was 10 degrees cooler than the surrounding drywall, when my A/C was blowing.

As for the dye, yes I had heard of that. My challenge now is that I thought that R-12 gauges could only be purchased by licensed A/C guys, so I never thought to try to buy my own gauge set, or companion vacuum pump.

Jeff

Stan's Customs

Quote: Oh well it's only time money and effort to do it all over again.

Like Larry said Jeff, these things did use a little refrigerant over a period of time back when, so you may have do a little every year.

...you can usually spot most significant leaks without dye, etc.

However, a sniffer is far better than the dye method if you want to get down to the nity gritty.

...and I guess you have found out that the only thing you can't buy without a license is the refrigerant itself. You "can" buy the equipment....and you already have plenty of refrigerant it seems..

Stan..

62Jeff

Yes I'm learning about the equipment. When I bought the 65 from my friend, he threw in the two 30lb containers of R-12, along with all of his spare parts, as part of the deal.

Stan's Customs

Wow, you can't beat a deal like that...Shouild last you a very long time.

I also got lucky last year and bought a 50lb. unopened drum from a friend for $300. It was his in his deceased grandfather's storage building.

I was going to retro fit some of my older stuff...but have changed my mind since I bought the big drum.....that should last me a very long time. Plus, you just can't beat the way R12 cools..

Stan...

62Jeff

We'll see how long it lasts. I've got 3 other cars that need to be repaired and charged up. I hope to have all 4 cars repaired and working before the first can is half-way gone.

Picture of said spare parts, loaded in the back of my 71 Vista Cruiser...

stingrayl76

Jeff,

On another but related subject, keep that freon/oil mix off the underside of the hood. That stuff can cause paint problems if allowed to permeate the underside of the hood.

Dave

62Jeff

Thanks, it was too late for my car by the time I bought it - paint bubbles were already present.

Once I fixed the A/C, and saw the wet stripe of oil on the hood after every drive, I installed an aftermarket oil shield. Now I just see a wet stripe of oil all over the fenderwells, hoses, and dripping off the oil shield.

mechron

harbor freight sells a gauge set that works fine for the older R-12 systems, i dropped my gauge set a couple of years ago and broke one, it was just cheaper to buy a new set than replace the gauge. the HF set if i recall is around $60 but sometimes on sale for $39.95, i waited until it was on sale then got an additional 10% useing one of their coupons.

OH, it comes in a nice plastic red carrying/storage case too.

62Jeff

Cool (pun intended). There's one of those close to my house.

I just looked them up, only found this one which speaks to R-134
http://www.harborfreight.com/cpi/cta...emnumber=92649