Hey all,

The AC was removed from our '77 when we purchased it, so I'm in the process of a putting in a completely new system (factory original with R12 - not interested in switching to R134). My goal is to get this all installed so I can get the car running again, and then take it to a shop for evacuation and charging.

I need some advice from you AC techs in the group. I know some of the basics about AC systems, but I really need some experienced direction with this project.

Everything is new (no re-manufactured parts). I have not installed the lines at this point, but the various components are mounted in place.

• AC Delco Professional R4 "pancake" style compressor (the compressor info shows it is compatible with R12 or R134A)
• stock style condenser
• all lines and hoses
• evap core
• accumulator
• green o-ring kit
• R12 freon (NOS cans - not reclaimed)

My questions:

1. How much oil will the system take in total? (not finding this in my AIM)
2. Do I add the total amount of oil directly to the compressor, or should I add some directly into the various areas (the accumulator as an example), OR do I just need to add the appropriate amount for the compressor and have the AC shop add the additional as they do the Freon charge?
3. Is it safe to run / drive the car without an AC charge in the system as long as I leave the compressor wiring unplugged so it doesn't actually engage the compressor?
4. I have read that I need Ester Oil for this system with R12. I'm unsure of the type of oil that came in the new compressor, so do I drain that out as best I can and replace with Ester oil?

I know this is a lot to ask, but it's important that I cover the details with this project. It was a big expense for us and I want to make sure I do this right the first time.

Adam

 

Adam,
I just went through this procedure on a '68 myself. The mineral oil can be added directly into the compressor since all components are new and absent of any existing oil.
Check the GM service manual for the later pancake R-4 style compressors total volume of oil. My A-6 compressor system calls for 11 ounces. That is way too much for the R-4 so check the manual.
The oil you need for R-12 is 525 AC Delco mineral oil. After adding it to the compressor turn the compressor by hand for several turns to move the oil around. It won't hurt it.
You may run the car with the system dry as long as the compressor is NOT engaged. A dry compressor may burn out. When a system leaks out all its refrigerant and you continue to operate the car that is essentially what happens as well as long as the AC is not run.
If you system started with R12 and was never converted to134a all old mineral oil maybe drained and new 525 mineral oil maybe replenished with the CORRECT VOLUME.
After you pull a vac. for an hour or longer let it sit with the gauges hooked up and monitor for a leak(s). If you are blessed not to have to chase a leak(s) than take one of your 12 or 14 ounce cans of R-12 and turn it upside down and let the vac. suck it in via the high side port. Remember we are not running the car yet. Once both gauges settle down high and low side pressures read same or close you may start the vehicle and charge with the remainder of the required weight of charge. The reason the car has to equalize after filling high side so the compressor doesn't slug due to liquid refrig.in the compressor. The assembly line charged them this way. Once the bubbles in the sight glass just disappear you are charged. Don't over charge like I did.
If you want to get some much better info than I can offer look for my thread on AC stuff under Marshal135. Some very knowledgeable people helped me along the way and are still helping me trouble shoot a problem I'm having with a possible new expansion valve that may be stuck in the open position, yes I said brand new part. The new stuff sucks.
Get going and let us know how you made out.
Marshal

 

my 79 was in service manual r4..(im not an ac tech)
heard from some forum posts..its in capacities of owners manual? 3# r12 11 ounces mineral oil.
im so paranoid (as i lost an r12 load from bad compressor new) that i pull vacuum as stated and prior to that i use compressed air and check both ways.. long vacuum to dry out and verify no leaks..i find r12 less prone to leakage
My questions:

1. How much oil will the system take in total? (not finding this in my AIM) check owner manual.. but i would STILL use gauges when filling
2. Do I add the total amount of oil directly to the compressor, or should I add some directly into the various areas (the accumulator as an example), OR do I just need to add the appropriate amount for the compressor and have the AC shop add the additional as they do the Freon charge? not sure ac shops still sell r12? if so let us know what you pay.. i would put in oil when assembling and split it condenser, accumulator, compressor and make sure not locked up as mentioned prior to use..i error on high side of amount
3. Is it safe to run / drive the car without an AC charge in the system as long as I leave the compressor wiring unplugged so it doesn't actually engage the compressor? it should be.. as low freon will not allow compressor to run..if it does you have another issue..
4. I have read that I need Ester Oil for this system with R12. I'm unsure of the type of oil that came in the new compressor, so do I drain that out as best I can and replace with Ester oil? drain compressor add a little mineral oil.. turn by hand let that drain..should be mineral oil

 

Thanks for the responses. I really appreciate the help with this.

Marshal - I checked my copy of the '77 GM service manual and it shows the R4 system takes 6oz of oil (the A6 system takes 11oz as you mentioned). Freon is listed as 3lb system capacity. I'll start by dumping out what oil came in the new compressor and adding in the new oil (just ordered a bottle of the ACDelco 15-117 - 525 viscosity oil). Once I get that taken care of, I'll pull a vacuum and see what happens before taking it to the shop to charge it. I may end up doing the R12 charge myself if I feel comfortable with it. It wouldn't be my first time, but it's been a few years since I did a system charge with a manifold gauge set. I also found your post about your AC system and you are right - some fantastic information there. Thanks for that.

Interpon - to answer your question about the shop having R12 - I doubt they do. I'm purchasing enough R12 from a friend to fill the system plus have enough on hand to refill one more time just in case. Given that it's getting harder to find, I paid $20 a can for it. which I'm fine with. Small expense in the overall project cost of this car rebuild project.

Thanks again,
Adam

 

Adam,
Glad to be able to forward the knowledge that was passed onto me during my ac project. It is rewarding to know you tackled it yourself. I chose to buy the gauges (Master Cool USA made) and do it myself. I believe I over filled mine as I got distracted by a neighbor who wanted to BS while I was filing the system with R12 and my darn weigh in scale times out automatically after 5 minutes. I wish I could disable that feature.
But to feel the system working again was rewarding. I have to recover some refrigerant out of my system and check my low side reading as it was high as well as do a feel test on the hoses as Lars shared in my post.
Just don't get distracted during the fill in and you should be ok. Yes the A-6 compressor is a beast at 11 ounces of oil and 3.25lbs of R-12. 6 ounces seems to jog my memory as being the correct oil amount for R-4 compressors.
Marshal

 

If you purchased a new compressor, it should be charged with oil, but verify. That is why they are saying the compressor can be used with R12 or R134A. The new POE or PAGA oil is compatible with both refrigerants, however the older mineral oil is not compatible with R134A.
If it were me and you have new components, I would charge the system with R134A. R134a is inexpensive. Lubricate all the O rings with PAGA oil when you install them. Be sure to evacuate the system for at least 1 to 2 hours to boil off any moisture in the system. Then Charge the system with refrigerant.
I am in the refrigeration business.