Getting ready to re-install my 70 A6 R12 AC system and need to ask some questions

[Michael L.]

Guys,

I'm getting ready to re-install the AC on my 70 GTO (yes I know but at least it's GM) and was hoping to get some questions answered. The system was removed for an engine rebuild a couple of years ago. It was a newly rebuilt compressor installed just a couple of years earlier and the entire system was overhauled at that time by a reputable AC shop in my area and was working fine before I removed it. I put it on my shelf while I rebuilt the engine and have been driving it a while and now I want to re-install it. It has not leaked any oil while on the shelf, but the system has been open to the atmosphere. I have already installed a new dryer. Can I assume the system still has sufficient oil or do I have to drain the compressor and start over? If I do have to drain it, I've read that the R12 oil uses mineral oil which I was able to source from my local NAPA, but I've also read that they switched to Ester oil for R12 systems? Can I just use the mineral oil? If I do drain it, I've read it takes 10.5 Oz of oil, does that sound correct? Do I just pour all 10.5 Oz into the compressor? I'm not actually going to be charging the system myself I'm going to have the shop do it but I want to install everything and have it ready to go so all they have to do is charge it when I give it to them. Thanks for any help you can give me.

Mike

[Mark E.]

Re: Getting ready to re-install my 70 A6 R12 AC system and need to ask some questions

Mike,

I love the look of the '70 GTO. I had a '69 RAIII 4-speed air car that I bought in college for $800. Different times.

Hopefully the compressor ports were plugged during storage. Otherwise, it may need to be checked after two years in storage. Definitely drain and refill its oil charge. The service manual has the procedure for doing this. It will also specify how much oil should be in the evaporator, condenser, dryer and POA.

While the system is open, it's cheap insurance to flush the system, and replace all the O-rings before adding oil. Use O-rings compatible with R134 as well as R12 to give you that option in the future. I recommend using a high quality synthetic ester oil designed for R12 and R134 systems. Installing the dryer is the last piece to install to minimize its exposure to moisture.

If you have a vacuum pump (not expensive) you can evacuate and check for leaks before taking it to the shop for charging.

[Bob I.]

Re: Getting ready to re-install my 70 A6 R12 AC system and need to ask some questions

Per the CSM, Corvettes AC systems require 11 ounces of oil. It also states oil quantities, for system components replacement, the Receiver-Dehydrator will require 1 ounce of oil.

[Michael L.]

Re: Getting ready to re-install my 70 A6 R12 AC system and need to ask some questions

Mark unfortunately the ports were not plugged they were open to air. I'll plan on draining the compressor and servicing the system as you suggest. I'll check out my CSM to see what the process is. I do have a vacuum pump and will see if I can figure out how to test the system before I take it to the shop. If I opt to use the ester oil does the system have to be completely purged of all traces of the old oil?

[Leif A.]

Re: Getting ready to re-install my 70 A6 R12 AC system and need to ask some questions

Michael,
Just so that you understand. Pulling a vacuum and holding a vacuum will only show that your system is not leaking under "vacuum pressure". When the system is charged, it will be experiencing pressures up to 70PSI pushing outward...completely different kind of pressure. You could have a leak free system under vacuum but still experience a leak under full charge.

[Michael L.]

Re: Getting ready to re-install my 70 A6 R12 AC system and need to ask some questions

OK thanks Leif good to know. I just read over the section on AC servicing in the CSM. Sounds like the compressor will get up to 6 Oz of oil and there can be an additional 5 Oz added of the Condenser, Evaporator, and dryer are replaced. I'm replacing the dryer but not replacing the condenser and evaporator but I will be flushing both of those. Does flushing and replacing count as the same thing? Would think the flush would effectively remove most of the oil that might be in those things so maybe I have to add that oil with flushing too? Also, can that extra oil for those things be poured into the compressor or do they have to be added directly into the other components?

[Leif A.]

Re: Getting ready to re-install my 70 A6 R12 AC system and need to ask some questions

Michael,
I'll let the experts like Larry Mulder answer those questions...he is my "go to" guy with A/C tech questions. Also, if Domenic happens along.

[Mark E.]

Re: Getting ready to re-install my 70 A6 R12 AC system and need to ask some questions

Yes, after flushing, replace the oil for that component. I add oil to each individual component. Do not fill the compressor beyond its own capacity.

[Michael L.]

Re: Getting ready to re-install my 70 A6 R12 AC system and need to ask some questions

Thanks Mark will do.