So I think we've got it narrowed down to either the VIR clogged or not functioning fully, or the condenser blocked somewhere.
I think my next steps will be to have the R12 recaptured, pull the VIR and have a look inside, and remove the condenser and clean and flush the heck out of it. Then reservice and see where I'm at.
I'll be back to update anyone interested in a follow-up, and I wanna thank everyone here for the advice, I feel like I have a much better understanding of ac from talking to you guys.

 

Great thread.... looking forward to updates. Getting ready to tackle this on my 71 and pre-planning just in case I run into issues.

 

I pulled the condenser and blew it out, it was totally clear, no issues there, so that rules that out. I decided to replace the VIR with a rebuilt unit, because I think by process of elimination, that is my issue. So Ive got it all tightened up and it's ready for service. Hope to get it serviced to this weekend and we'll see how it does.

 

So I think Im pulling the plug on this one and moving on to something else. I might take it to a shop and get their opinion, or just roll through the summer with no a/c and maybe look at a Vintage Air next summer.

Just to recap where it sits, compressor is rebuilt new, VIR is rebuilt new, evaporator was removed, cleaned and flushed, the condensor was removed, cleaned and flushed, all lines flushed, all orings replaced. I removed the compressor again and drained and reserviced with 10.5 oz of ester. I pulled a vacuum for over an hour, and let it sit all day and it held.

This time we serviced it with 3lbs of refrigerant. Temp was hot yesterday, about 94* and humid. Idling at 1100 with compressor running. System pressures were at 45/275, vent temps were down to 50*. As usual, misting water on the compressor would bring the pressures down right away. Suction line is cold. Evaporator lines are sweating. Figured we'd take it out and get some good airflow through the condensor and see what it did. Backed out of the driveway, put it in 1st, gave it a little clutch and the belt started slipping right away, brought it back in, turned it back on, and belt is slipping. Misted the condensor, and it was happy again.

Ok, so maybe an over charge situation. Removed some charge, System pressures 40/260. Vent temps 59*. Backed it out, got it to the end of the block, belt slip. Misted the condensor, and its normal again. I did notice if i ran the RPM up the pressures would drop, then back to idle, at this point the belt slip would kind of start, not fully but just starting to slip and then back to normal.

Ok, lets try to sneak up on the right charge. Removed charge, pressures down to 15/210. Vent temps 80*. Add some charge, little at a time, stopping and letting it run then more, until we're 25/250. Vent temps are 68*, but if i give it some RPM, temps come down to 60*. No slip even with RPM, no problem. Back it out, this time im on the main road, 55 MPH, temps are running upper to mid 50s, and its pretty pleasant in the cabin. Could be colder, but its nice. Maybe 3 mins down the road, come to a stop and belt starts to slip. Rest of the drive if i turn it on, it slips right away. Of course when i get back and mist it, it runs again normal.

Remove a little more charge, and same story, belt starts to slip eventually, but now we're running almost 70* vent temps, so even if it worked whats the point?

So basically, condensor isnt plugged, i cleaned it, flushed it, compressed air, its clear. Same with the evaporator. VIR is new rebuilt. Cant be overcharged, ive tried it full, low, and every charge in between. Compressor is new rebuilt and serviced up with plenty of oil. Belt is tight. Vacuumed the system out, it shouldnt have any air or moisture. Dont know where to go from here.

 

Good news though, I drove 30 mins to a friend's house who had R12 and a machine to do all this. All the way there, on a really hot sweaty Georgia day, it ran great, didn't get overheat one bit. Even sitting in the driveway, idling forever while we fiddled with it, running the RPMs up and down and sitting, water temp never even touched 200*. So I'll take that as a small victory.

 

really weird.
oil sounds wrong.

 

Yea 🤷
I pulled the compressor off and drained and refilled the oil just to make sure sure it was correct. I know it's making it's way around the system. Eh.

 

for some reason pag oil is messing with my brain.
and mineral for r-12?

 

That's what I read.
PAG for R134
mineral for R12
Ester works for both.
​​​

 

I don't remember seeing any receiver/drier changing.
I would change that, flush oil, pick a gas and use specific oil for the gas.

 

Yea this is the same thing my buddy helping me couldnt wrap his head around. It's all the in VIR unit. Dryer, the accumulator, the expansion valve, the POV, it's all in the VIR. And that's new.

 

if the belt squeals it's too loose ,

 

The belt doesnt squeak, the compressor locks up at certain times and the belt slips around the pulley and screams and burns. Kind of a different thing.

 

Frustrating, these gremlins. The only moving parts in your system are the compressor and vir, soooooo one of them has to be the culprit.

I have never seen a compressor that "locks up" that was in proper working order. I am beginning to suspect you got a crap compressor. (And I can't understand why you insist on NOT using mineral oil.)
VS

 

Frustrating, these gremlins. The only moving parts in your system are the compressor and vir, soooooo one of them has to be the culprit.
True, makes sense. Or a clog somewhere, but i hopefully ruled that out. Or incorrect service, but hopefully i ruled that out too.

I have never seen a compressor that "locks up" that was in proper working order. I am beginning to suspect you got a crap compressor.
Definitely possible. Old compressor was acting the same way, so i kinda figured it must be something external to the compressor causing the issue. Plus, it pumps and cools, and when it does start to lock, misting the condensor frees it up and it works again. Seems like an internally failed compressor wouldnt free up with water on the condensor, but stranger things have happened.

(And I can't understand why you insist on NOT using mineral oil.)
Definitely not against it. I just have a bunch of ester oil here on hand, and everything ive seen and read, including the bottle, says its compatible and usable with R12 and R134 both, so i didnt see an issue using it. If i saw anything that says it might be a problem, i would have for sure not used it.

 

Think I would try returning that compressor. Tell em it locks up.

Is it an R4 type?
(My 69 has an A6 which is said to be pretty bulletproof.). I wish "Domenic" would add his thoughts to this thread.

Is it possible to buy a new compressor and not a rebuild?

VS

 

Its an A6.

 

Excellent!
I have heard that the NEW A6 substitute that Old Air sells is an excellent unit. (If you did not know, the corvette A6 is a bit shorter than other A6 compressors. There is a small spacer to make up for this on the oem A6)
Talk to those guys. They are very friendly. Believe they are in Fort Worth.

Keep after it! You will beat the gremlins!!


VS

 

When the Compressor starts locking up and belt smoking , does this cause the engine to want to die at Idle speed ?

It is the belt smoking and not the AC Clutch correct ?

 

I hope so! Just the few minute drive i had the other day where the A/C actually worked was motivating.