A/C compressor and freon ?

[Daves72'GMC]

I'm almost done restoring my 72' GMC 402BB and it's time to recharge the factory A/C which was blowing cool air before the restoration. My ? is I've put new A/C hoses on and was wondering if I should charge the system with R-12 or freeze 12? and my other ? is should I replace the origional A/C compressor with a rebuilt one before I spend alot of money recharging the system or should I use the origional one and take a chance that the origional one is fine and charge the system? Thank you for all of your help.

[sneakysnake]

It comes down to money. If it was working before you could just recharge with freeze 12 or Hotshot. If you change the compressor, then change the oil,filter dryer and convert it to 134.

[mrein3]

No matter which way you go you need a new receiver/dryer. If you go R134a you need to get on that is compatible with R134a (I don't know the difference but when buying a replacement some say compatible with R134a)

[WorkinLonghorn]

Regarding "freeze 12". I'm not sure exactly what this stuff is composed of,but the label says "not approved by EPA" (or something to that effect). In the instructions it says you have to install a high-side relief valve. I didn't (in my car) and headed out across the desert,5+ hours at 100++,and it blew out the seal in the compressor.So I have to believe that that relief valve really is necessary.

[Daves72'GMC]

what is hotshot?

[Daves72'GMC]

Ttt

[sneakysnake]

Originally Posted by Daves72'GMC

what is hotshot?

http://www.icorinternational.com/hotshot.html

It comes in small cans too

[Bob B.]

You could write a book on this subject! I can tell you what worked for my '67. First off, I have no experience with Freeze-12, Fridgid-12, Hotshot, or any other R-12 substitute. I am not saying they are bad or good, just that I don't use them. I converted my '67 to R-134a. When doing a 134 conversion, there are a few things you need to do in order to have good results. First off, the compressor: cheap rebuilt A6 compressors are no bargain. If you need a compressor, buy a quality rebuilt. AC-Delco sells good rebuilts and brand new compressors if you want to spend the coin. In order that you comprssor lasts, it must have oil. The type of oil in an R-12 system will not work with 134. The problem is that the mineral oil used in an R-12 system will not mix with 134, and thus will not circulate through the system. You can either have your system flushed or if it is apart, just drain as much oil out of your compressor as you can. It doesn't matter if a little trace is left in it. Replace the oil with the specified amount of 134 compatable oil. The 2 most commonly used are PAG and Esther (sometimes called POE). I like Esther a bit better in old systems. Next part that needs attention is the receiver-drier. As noted in the above posts, a drier for an R-12 system will not work with 134. It should be changed. Hoses need to be changed as well, with hoses that are 134 compatable. 134 can actually permiate R-12 hose. You might get by with R-12 hoses if they are in good shape, but you will probably need to recharge the system often. The valves are another issue. There are 2 valves. The expansion valve, with is on the inlet side of the evaporator, and the POA valve. The POA is the large cylindrical valve that is mounted along side the evaporator case, plumbed in the outlet side of the evaporator. The good news is that the expansion valve is cheap and available just about everywhere. The bad news is the POA valve is no longer made and very expensive if you find an NOS one (I got lucky). When changing to 134, the expansion valve requires no modification, it will work great right out of the box. Just be sure that the sensing bulb is clamped securly to the evaporator outlet pipe, and wrapped with insulating tape. The POA is a differnent story. This valve regulates pressure in the evaporator, and since 134 operates at a bit higher pressure that R-12, the POA valve should be adjusted. The forum on this site explains how:
http://www.ackits.com/
You can get by without adjusting the POA valve, the system will just not get quite as cold as it did with R-12. You may have seen a 'POA eliminator kit'. What that is is a pipe that eliminates the POA valve with a pressure switch in it. This kit controls the pressure in the evaporator by cycling the compressor on and off, much like a modern system. I have heard good and bad about those, but my feeling is that the A6 compressor wasn't really designed for a cycling system. Now some say that for best results you should change the evaporator and condensor as well. In my case my condensor was shot anyway, and my evaporator had bad threads on one fitting. I think you might get by without changing these parts if they are in good shape, but they should be flushed. When converting to 134, it is a good idea to get the best airflow possible through the condensor. Use a fan shroud and a good fan. I use a 6 blade steel fan (NOT a flex-fan) with no clutch. It's a bit noisey, but it works well. Although I spent quite a bit of money, I got very good results converting to R-134a.

[badpeanut]

Good info Bob B.! I'm having mine converted to R-134a soon.

[truckdude239]

be sure to pujll a good vacuum before you charge it

[Andy4639]

I've had my 134-A system now for almost 7 years. 5 of those it had the old C-6 compressor and I went through 3 of them. 2 Brand new ones and 1 rebuilt for 134-A freon and they just didn't hold up. I swaped to the little Sandon compressor and it works great. Do yourself a favor and swap. In the long run it will be cheaper.
I did away with the POA valve also since I went to the later model system. I used my fire wall box but put a late model evaperator inside it.
The temp. gets down to 38 degree's while moving and around 48 when sitting still this is one of the draw backs of 134-A but I also need to do a electric fan install to help with it. I have a small electric fan but it doesn't pull enough to help when sitting still.