I dont know anything about A/C, but I decided to tinker with my original R12 system. The PO said it worked, but needed to be recharged. I replaced all the orings, removed, cleaned, and replaced the desiccant in the VIR, removed and cleaned the evaporator, and flushed out the condenser. I replaced the compressor with a reman from Summit, and filled it with 10.5 oz of ester oil. Flushed the system out, pulled a vacuum, and it held, so i serviced it up with 3lbs of R12.
It runs and gets cool, and all is well, until about 10 mins into the drive. The belt on the compressor starts slipping and burning and smoking. Im guessing the compressor gets hard to turn. If i open the hood, i can see that the clutch is engaged and its turning a little, but the belt is just slipping around and making all kinds of noise. If i stop and wait until everything cools down under the hood, its fine and runs normal again.
So, A/C guys, does this mean it needs more R12? or too much? or more oil? Or should i just quit screwing around with it and take it to someone who knows?

While running, its at about 50 on the low side and 280ish on the high.

 

What year? I think the oil to use is mineral oil with r12..ester oil is usually used when transitioning from r12 134..
what year may help others diagnose.
i would tighten the belt more and see if that cures it..it needs to be tighter than u think..

 

Oops sorry, 1975.

 

Sounds like you serviced it correctly. If anything slightly lower than the 11oz oil and 3.25lbs of freon that I'm aware of.
I'd tighten up the belt a bit or better yet get a new belt as now the one you have is glazed from slipping.
mineral oil is the compatible oil for r12, but ester is also compatible and would work fine.

 

You say you put the oil in then flushed the system out. I assume you didn't flush the oil out!

 

All due respect, but I think your first sentence describes your problem. The a/c system in your '75 is not complicated but you should know at least the basics before trying repairs. Doing things incorrectly can damage not only the system but you also. For example, did you bleed the air from the hose before charging the system? If not, that can damage components as air has moisture in it which is an arch enemy of a/c systems. More important, if you get freon in your eyes, you'll have some real problems.

FWIW, I got tired of paying to have my a/c system repaired so I took a couple of adult education courses on the subject at the local high school. That has saved me some serious $ over the years.

 

first as mentioned ester oil is not the correct oil for true r12 refrigerant,
you need to get the pressure readings and post them so we can see what they are while idling and when the compressor stops turning,
what part of the country do you live in and what]s the temps and humidity?

Neal

 

Im on belt #3, they all do the same. First 2 were 7/16 wide, and the one on now is a 1/2, it has more meat and fits the pulley perfect. Though maybe a stouter belt would do better, but does the same thing. Got it pretty tight, but can always try to get a little more on it.

 

After all as stated above.Did you evacuate with a pump?

 

That does look weird.
No, i removed the compressor, evap and VIR, flushed the lines and the condenser out, and flushed the parts, replaced orings, added oil and reinstalled.

 

The bottle and everything i read online says Ester is good for R12 and R134. I guess mineral oil is the true oil for R12, but Ester should work right?

Ill get those pressures for you. I wasnt sure what info was needed to really troubleshoot it. Thanks for taking a look.

Im in Georgia, so yesterday it was pretty sweaty, shows 90* and 53% humidity when i was running it.

 

Yes indeed i did.

 

Sounds like something is not right. Overcharged I would say if I had to take a guess. You sure about the oil and freon quantities?

 

The oil in the compressor is definitely right; i drained what came in it and added exactly 10.5 oz.
The specs say 3 lbs of freon, 48oz....i added 4 cans of 12oz each into it, so i should be right at 3 lbs.

 

Post up some pics..like how the belt sits in pulley etc..
pressures are high but maybe not if really hot and humid..

it is also possible the remanufactured compressor is crap too..

 

What condition are the radiator seals?
Are you still running the OEM mechanical fan and shroud?

280 psi for an r12 system is a little high, typically if the charge is correct the suction line will be cold at the compressor which will help reduce the head pressure.
corvettes are already challenged as for as airflow through the radiator so the seals, fan shroud and the fan clutch all need to be in top shape
I'm in south Louisiana, usually 90* plus with 75% humidity plus, an r12 system would typically be around 180 to 220 psi with decent air flow across the condenser
50 psi on the suction from a system that has a VIR is an indication that something is not right, the VIR should control the evaporator pressure at 28 to 31 psi.

Can you try putting a big fan blowing at the front of the car (a blower is better if you have one) to help with airflow while watching the pressures? Having the hood all the way open will hamper the airflow to the condenser also, I try to prop the hood about half way open when troubleshooting the AC along with a blower blowing into the lower area of the front of the car.

50 psi on the suction and 280 psi on the discharge from a car with a VIR would lead me to think that there is air/moisture in the system,

Hope this helps,

Neal,

 

 

Yep mechanical fan and shroud.
I did have the hood open and car in the garage while I was testing the pressure. I'll definitely try the hood down fan blowing into the condenser trick. I'll report what the pressures are with that set up.
Thanks for the lead, it's cool to be able to come here and get some guidance when you're out of ideas.

 

or use a hose to wet condenser...and check pressures..
that belt i think still loose..

 

Looks like that clutch got hot with the cooked looking paint. I'm not at home so I can't compare the tightness of my belt to what you're showing. I'd have to agree that it does still look too loose. Are you all out of adjustment travel to make it tighter?