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Little help from fellow DIYers

75sled on Thu July 10, 2008 3:54 PM User is offlineView users profile

Year: 1975
Make: Cadillac
Model: Deville
Engine Size: 500
Refrigerant Type: r12
Country of Origin: United States

Hey guys, I need a little guidance here. I am a complete newbie when it comes to AC systems. I have a 75 Cadillac that needs the AC system basically rebuilt. I took it to a local shop and the guy shot a little freon/freeze12 to it and it came right out the back of the compressor. As I had figured I need a new compressor. Now, the mechanic said that if he were to do it, he would change out the VIR assembly with something else (can't remember what he said now) and "add" a switch that would make the compressor cycle rather than running constantly. Sounds like a good idea to me, but it will take $800 to do it. Now I figured that wasn't way out of line, but it is way out of budget. I would like to do this on my own so that is where I need your help.

I would like to know first off, if anyone else has done this on their older AC system and if it is dependable or not. I would also like to know what parts I need to replace (aside from the compressor) and exactly how to connect this "switch". I realize the system will need to be flushed once I have it apart, but that is about all I know about doing this. Also, it would be great to hear what y'all think as far as which parts are a definite "replace" and which ones could be left alone when doing something like this.

I am very mechanically inclined and feel that this in not beyond me. I just need some procedures to follow and maybe a little guidance and some tricks of the trade.

Dave in Texas on Thu July 10, 2008 6:37 PM User is offlineView users profile

Look for the 'navigation' link at the bottom of the page. Click on AC procedures. Read all the info and you will get a good idea of auto AC.

Bringing a 33yr old system back to life will be a challange, but it's not all that mysterious. A 'project' to be sure, but worthwhile.

At 2, I went home with a 10. At 10 I woke up with a 2 !!

fonebone on Fri July 11, 2008 3:03 AM User is offline

I drive a '79 Caprice as a daily driver with a VIR unit, and it will freeze you out of the car. Back about '87 or so, I took a complete VIR assy., evaporator and all, out of a '74 Monte Carlo.I'm still using it, and it works great. My original setup was CCOT setup from the factory. That stands for Cycling Clutch, Orifice Tube. The reason I was replacing it was that the clutch was blown on the compressor, a common problem. These Harrison A-6 compressors were not designed to constantly cycle--- too small area on the clutch overheats them. Leave your VIR system in there. I went to GM school on that system, and it's a good one. Buy a VIR desiccant kit for it. Plenty out there, about 20 bucks. Change the bag in the can that hangs on the unit. Take out the screws. CAREFULLY pry the can off, it will be on there tight. Discard the old bag, stuff the new one in, slid off the old filter, put the new one on the pickup tube. . Change both "O" rings. One sits at the base, has a different shape. Use Nylog lube, available on this site, to lube the "O" rings. Add an ounce of r-12 mineral oil into the can. If you do not know what this is, find out now. I think this is available here. Clean the inner surface where the "O" rings seal. It MUST be clean AND smooth!!! Lube rings generously with Nylog lube. Push it back on, reattach the screws. Take off the compressor. Remove the drain plug. Pour as much as will come out into a cheap kitchen measuring cup. If it's under 4 oz., add 5 oz. of fresh r-12 mineral oil into the back ports of the new compressor. Slowly turn it with a finger over the ports to feel which one is sucking in. Put it a little at a time in that port till it's all in there. The total is ten, but remember you added 1 oz. into the can with the bag, so it's 9 oz. total. Put new "O" rings that fit the back connection flange (available here) with Nylog lube, reattach hose block assy, to back of compressor. Pull a deep vacuum, add the amount called for of R-12 as noted on your original compressor, probably 3 to 4 lbs. Check system operation. If you did it right, it will cool nicely. Let's hear your results, O.K.?

fonebone on Fri July 11, 2008 3:11 AM User is offline

I forgot to ask if the leak at the back of the compressor was a leaking "O" ring , or was it coming out of the case? These are tough compressors, acknowledged by many as THE best ever designed. DO NOT replace it until you confirm where that leak was coming from. Have him check it again to affirm where it is coming from. An original compressor on your car, in good shape, is better than any replacement!

75sled on Fri July 11, 2008 9:27 AM User is offlineView users profile

Fonebone you are "The man". This is exactly the sort of information I was looking for. I am not 100% that the leak was at the seal, but I am pretty sure that is what he said. I will infact check it myself and see exactly where it is coming from. I will keep you guys updated, however, this is a work in progress. I can only do it when I have the funds. But I plan to start soon, as I am not really a fan of riding with the windows down. And here in Alabama The Beautiful, it is either that or die...without AC. I don't have any reason to believe that there is anything wrong with my VIR. Is there something I should look for in terms of determining it's usability? I think the mechanic suggested this new setup mostly because he wasn't a fan of the VIR. He is an older gentleman, and has been working on these things at least since mine was new. So I don't really know where he is coming from on this.

While I am asking, what are your thoughts on the Freeze 12 for this system? Is it any good, are there expected problems, etc.?

75sled on Fri July 11, 2008 9:35 AM User is offlineView users profile

Oh yeah, you mentioned that these old compressors were better than any replacement. I printed out directions on how to rebuild one, but then read of it not being very reliable after the fact. Do you recommend rebuilding this compressor or replacing it if it is leaking at the seal?

75sled on Fri July 11, 2008 1:05 PM User is offlineView users profile

Oh yeah. I can't believe I forgot to ask. I have an '03 GMC Yukon XL. The system cools just fine, but my compressor is making an awful noise. I will have to replace it, but since the system works fine my plan was to only replace the compressor then have it evacuated and recharged. Is there any suggestions as to other things that need to be replaced due to age/mileage. The truck has about 103k on it and like I mentioned the AC still cools very well.

I assume the procedure for this would be the same as the cadillac. Once I have the compressor off to drain the oil to measure it and replace exactly the amount that was measured pouring it straight into the new compressor.

Also, where do you guys recommend buying these parts? For the GMC and the Cadillac. I am looking for decent quality at a GOOD price.

Chick on Fri July 11, 2008 6:49 PM User is offlineView users profile

You won't get all the oil out of the compressor, so add back an extra ounce from what you drain, The compressor works fine now, but will begin to spill it's innards into the system, so change as soon as possible, and don't use it until you do. Otherwise you will be changing other parts along with it. Change the drier, expansion device..The best place in the internet to get parts is right here.. If you don't see what you need, doesn't mean they don't have it..Not everything is on their website. So just e-mail them if you need anything else at Hope this helps..

Email: Chick


Freedoms just another word for nothing left to lose

fonebone on Fri July 11, 2008 7:29 PM User is offline

Hi 75sled; Do not use ANYTHING but pure r-12 Freon!!!!! It is a little pricey, but it's coming down. Your VIR unit is a sealed unit, and unless it sat around wide open with no hoses, it will be fine. My unit came out of a boneyard, who knows how long it was there, but it was sealed, not opened, and it runs great, even after all these years. . Some folks who worked on these did not like them, not sure why. All the ones I saw were trouble free, and I saw a bunch. I was a mechanic on these the entire production run, till the cycling clutch replaced them. It was cost that made them go to the CCOT system----much cheaper, not as good. On your compressor--again, do not replace it unless you confirm absolutely that it is an internal problem. This is a very complicated, precision unit to rebuild, and requires many special tools. If you must replace it, inquire here to the PROS where to buy a rebuild. As for the seals in the back end, they are just common compressor "O" rings available here, You just put them into the grooves at the back of the compressor. It will be seen when you disconnect the hose block assy. from the back end. They go between the hose block and the end case. This is not a CASE, or BODY seal we're talking about I hope. If so, then plan on a rebuild. Take off the compressor and carefully inspect it. If it looks like the case is leaking, then it's rebuild time. But VERIFY before you do anything. I don't know if these compressors are still available new. Inquire,as Chick says, at for more info.

fonebone on Fri July 11, 2008 8:26 PM User is offline

75sled--Chick is "the man" on anything new, as you can see from my lack of reply on your newer vehicle! By the way, unless the compressor is shot and has passed debris through the system(highly unlikely with this system), I see no need for a flush. These A-6 Frigidaire units have an internal oil pump and stayed lubed. If it turns over quietly by hand with no roughness, you are good to go.

Edited: Sat July 12, 2008 at 1:04 AM by fonebone

75sled on Mon July 14, 2008 3:13 PM User is offlineView users profile

Thanks all. I will let you know how it comes out. BTW, I love this forum. So far you guys have given me a wealth of information....valuable information.

JJM on Wed July 16, 2008 3:24 AM User is offline

Absolutely do not go with an VIR eliminator, silly switches, and other junk... your system was among the best before downsizing and cost saving beginning in 1977 became the norm.

Usually those who want to "eliminate" do so because they don't know enough about the system. Either find someone who does, or better yet, get the tools and help you need here and get it done right.

The leak out the back could also be a pressure relief valve, or the superheat switch - both pretty easy fixes, though finding the correct ones can be a bit of pain.

Flush, hoses, fan clutch, replacing the VIR desiccant, and all O-rings and you should be good to go.


When considering your next auto A/C purchase, please consider the site that supports you:

NickD on Wed July 16, 2008 10:30 AM User is offline

Really loved the climate control in those cars, a one transistor circuit for the bend door motor, rest was all electro-mechanical so you could watch what it was doing. The three I had back in those years just needed a good cleaning and a few drops of oil here and there and were easy to remove for servicing.

One bad thing about this old stuff is that rubber rots with age, no matter how well it's cared for, more than likely a bad O ring for the pressure relief valve. I sure had to change a lot of rubber in my 82 Chevy motor home, seals, vacuum, fuel, hydraulic lines, O ring's, etc., parts cost was cheap, but so was the labor, I only pay myself 2 cents an hour, but was extremely labor intensive work.

You must have the 472, not exactly great on fuel economy, 12-15 mpg was tops on the highway, was lucky to do 6-7 around town, recall the tank size was around 27 gallons, would cost around 110 bucks to fill it.

75sled on Thu July 24, 2008 3:31 PM User is offlineView users profile

Sorry for the blank message. My bad.

Nick you are right on all accounts except the displacement is 500ci. But about 13.5 is all i can get and the pump shuts off at $100 with a debit card so i am sure it would take another $10 or so. But it is fun to drive, and hey it cost me less to drive that than if i had a small car with a car payment and full coverage insurance.

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