Matty Gritt

Hey guys, I recently overhauled the entire AC system on my 78 Corvette yesterday. I had ordered all new parts. The entire system is brand new. I rebuilt my AC box, installed new metal lines going to the condenser (including the service port going to the evaporator), and I purchased a brand new AC Compressor.

After looking at tons of topics and guides before beginning this overhaul I finally decided I was ready. Yesterday I finished putting everything together and I vacuumed out the system for about 45 minutes. I let it then sit for another 45. All good! No loss in pressure. I charged the system using 36 oz of R134. It blows ice cold in my cabin and the system seems to be running fine until I feel the compressor and it is BURNING hot. I cant even touch it, it's so hot. I dont want to burn out the compressor.

Anyone have any ideas why it would do this? The compressor was oiled with 3 oz of PAG 150 oil, and I also added 3 oz of PAG 150 oil into the accumulator before installing. Do I need more oil? All the guides I have found have shown 6 oz of oil needed in the system.

Any help is appreciated! I was so excited to have air conditioning... but it's never easy with these Corvettes!

mikem350

Well, as long as you vacuumed and added oil, and the system is COLD...AND pressures are OK...enjoy the chill!!


Yes compressors run hot. THey are doing a LOT of work. Everything under the hood gets hot. Try touching the alternator after car has been running for a while.

REELAV8R

6 OZ of PAG 150 is correct so you should be fine.
Compressors put together in China though so...time will tell.

Learning_Curve

Most modern cars use 1-1.5 pounds of R134. You may be overcharged. Do you have gauges? You should be 30-40 psi low side and 150-250 high side. Depends on how hot it is outside when running.

Big2Bird

My 81 takes 3 lb of R12. I think with 134 you use 10% less.
Yes compressors run hot as a pistol. Just drive the car and enjoy.

Matty Gritt

Thanks for all the replies guys. I guess I'll just take the car out and enjoy it. I didn't expect it to as hot to the touch as it was. If it gets as hot as a piston thats pretty hot. I read to put in 80% of the amount of R12. The service tag on the original compressor indicated 3.75 lbs of R12. So I figured 80% of that would be 36oz. I dont think its overcharged. I'm going to drive it and try it out. Hopefully itll hold up. The temps inside the car were phenomenal. The compressor has a 2 year warranty so hopefully if it goes... its before that

REELAV8R

Do you happen to remember which orifice tube you used, color or size? It's not related to your compressor temps, just curious.
Have you measured the duct temps?
Are you using stock components , condenser stock or replacement parallel flow?

Matty Gritt

Yeah, so my orifice tube was was white colored orifice tube. Its size looked to be pretty standard from what I've seen of orifice tubes. If you want to check it out, I purchased it from AutoZone, Part # MT0097-1 .

So I'm using some stock components and some not stock. Stock components I used were the Accumulator, Evaporator Core (although I purchased the core for a 1980 because it was like $200 cheaper; it works, I just had to slighly flex the soft aluminum of the line the orifice tube goes into).

The condenser I used was from Ebay and looks to be like a Chinese replica. The Compressor I ordered was a 4 Seasons compressor new from AutoZone... kinda wishing I had bought the AC Delco one now though. I also replaced all my switches and they are Santech (the cycling switch and the thermostatic switch). The metal lines I ordered from a corvette specialty shop. The rubber muffler hose to the compressor is also 4 Seasons.

Note about the condenser is mine did not have the correct bends for the metal line to the accumulator. It's very soft metal though so you can tweak it. Took me about 7 hours yesterday to fix it all together. I used butyl caulking from Amazon to seal the AC box as well and then I used butyl tape to cover the joints on the box.

Hope this helps!

REELAV8R

Yes helps a lot, thanks!
That orfice tube is the santech .072" orifice. If it's working good that's great.
You condenser, is it parallel flow or do you know for sure one way or the other?
The reason I ask is the parallel flow combined with the .072 orifice may be a winner if it's working well for you.
So far I'm under the impression that the .067 blue ford is a better orifice tube or maybe even the ford red .062. However if yours is working well then that may not be true. Or it may be true with stock condensers vs the parallel flow condensers.
Duct temp vs outside air temp is really the true test of the system, especially once humidity rises above 50%. If you can keep that duct temp low even at idle, that's what everyone wants.

fishslayer143

do you have the stock mechanical cooling fan or did you use electrics?..If you have electrics, one needs to run as soon as you turn on A/C ..

Matty Gritt

Glad I can help! The AC system is such an overhaul that Im glad I can help. Not sure on my condenser, I do not think it's a parallel flow condenser. It looks basically identical to the stock condenser with the exception of the tube at the bottom. Yeah yesterday when I got it running it was pretty humid and warm out. It made the inside extremely cold. It was like nothing I've experienced with my Vette, used to having my back sweat like crazy

Only other thing that i am not sure about is there is a lot of condensation coming out of the bottom of my AC box. But hopefully thats a sign that its producing a lot of cold temps. Hope this helps! If you need any links to the parts I ordered just send me a message!

And yes, I do have my mechanical fan still. I haven't and don't really plan on converting to electric fans! I enjoy the good old mechanical fan.

Bigguyinmo

I had an R134 conversion done on my '75. It bows cool not cold, but the compressor put a load on my 350. If I am holding rpm at 1000 and turn on AC my rpm drops to 500 even driving at 70 mph if I turn it on I feel a drop in rpm. Does yours do that?

REELAV8R

I would guess your system is overcharged and your pressures (high and low) are running pretty high. Check the low pressure,if it's running over 50 it's overcharged, unless it's 110* outside that is. Running too high over time can damage the pump.