: A/C Conversion, A6 -> R4



69CDV
03-11-05, 11:24 AM
Since summer is coming up quick here in Arizona and I'm still stuck with no A/C in my Coupe deVille, I'm wondering as to what can all be done to get all the work done at once. I'm seeing some billet parts for the big Cad engines, namely a set of A/C and alternator brackets. What's appealing about the A/C bracket is that it allows you to use whatever intake manifold you'd want, increasing aftermarket potential. Now the stickler... It's made for an R4 compressor, whereas my '69 has got an old A6 style compressor on it.

Are there any real other benefits to going with the new "short-fat" style compressor? Better cooling? Faster cool-down period? Less maintainence?

In addition to the new compressor and refridgerant, what am I going to need to upgrade my old '69 deVille's aged A/C to a new R134 system?

*Note*
I'm finding remanufactured R4 compressors with a single groove pulley ('89 Fleetwood Brougham) are going for around $110 at local auto-parts stores. Then I'm seeing them with serpentine pulleys going for $40'ish on eBay... How much should one of these really go for?
*/Note*

Big_Blue
03-11-05, 08:05 PM
I never changed my compressor when I converted to R134a from R12. I just changed the accumlator or how ever its spelled. I took my compressor off and kept it up side down while I constantly flushed it out with R134a oil. I did that a couple of times. Put everthing back and then evac'ed the system and put in 2.8 Lbs of r134. Hasnt failed since even tho I am a few ounces under the conversion


I purchased the r134 convert kit $40,Accumlator $55 and 20 bucks for the evac and 2 cans extra of r134.

N0DIH
03-12-05, 02:40 PM
Are there any real other benefits to going with the new "short-fat" style compressor? Better cooling? Faster cool-down period? Less maintainence?


Less HP draw when on (like 45 hp vs 65 is what I have always heard, but that sounds like a lot if you ask me)
Less rotating mass to turn, so better acceleration w/AC on
Less cyls, the A6 is a 6 cyl compressor, the R4 is a 4 cyl. As for how much actual flow change, I don't know.

You might find the brackets from a 368 to fit the R4 on the older Cad V8's. But I don't know for sure if the 368's ever got the R4 compressor. You might be able to adapt some Olds brackets from the 307, but they mount it on the passenger side if that is a problem.

Tom

69CDV
03-12-05, 04:48 PM
Aha, so there *are* a few good reasons to go with the R4. Definately good news.

Now for the biggest fear... How much of the current R12 system am I going to have to swap out to accomodate this new compressor? Hoses, fittings, etc?

N0DIH
03-12-05, 06:46 PM
The compressor doesn't know if it is R134a or R12, or even R22, or R116 for that matter. In reality you don't need to change anything with the newer retrofit kits. Some say that you must clean out the system and such, but I have not on 3 cars now and not a one has had an issue.

Now, that be said. There is a lot of oil that is in the dessicant in the accumulator, so that would be the only thing that should be replaced, and it can't hurt to flush it, but I haven't, I just vacuumed it down (the get the water out, as water boils at a higher temp under pressure, the converse is it boils at a MUCH lower temp in a vacuum. Hence it will be able to be removed when it is under a vacuum. Water is probably the most damaging thing in an AC system. I made a homebrew vacuum sysstem from a handheld vacuum pump and a T and use the engine as the main pump. Once it got statble at the lowest pressure I could get, I vicegripped off the engine line, and started hand pumping to around 28-29 inches. It takes a while. If it is taking a long time it means you still have more water in there. You cannot vacuum it down at all if there is water in the system. Once the water is removed, it will start to get lower and lower in vacuum.

Just remember one thing, the compressor can only compress a gas, if it tries to compress a liquid, it will destroy the compressor. So too much freon, or water, or oil will damage it. The oil is critical to have (it is carried as a vapor in the freon), if not, the compressor will run it dry and wear out quickly as well as be noisy.

the R134a Retrofits at Walmart and such are not a bad deal ($30-$35), they worked fine for me, just get one that has BRASS fittings. I had a plastic one blow off in my face, it wasn't very fun. Or at least buy a charging hose that has a brass end on both sides.

Another low cost recommendation was since i had already got a kit that had a low side gauge (gauges are very important), Mejiers (a local chain like Walmart that is expanding from the Grand Rapids area of Michigan) has a gauge that is low side AND high side, it has an adapter that you can connect to either side (one at a time) and read the high side pressures. This will allow you to accurately gauge your pressures to ensure you have a good running system. You don't want to over pressure it. (broken comprssors result...)

A note I have heard, is most documentation states that you put in 85% of the freon that the system called out for when it was R12 as R134a. That statement isn't always true, use your gauges on the high and low and use that instead of weight. You will need temp charts from the cars original and a R134a system that is similar to make a good judgement of what pressures to run. Mine have all been closer to 1:1 R12-R134a with excellent results.

Tom

tripleyellow78cad
03-13-05, 12:26 AM
Less HP draw when on (like 45 hp vs 65 is what I have always heard, but that sounds like a lot if you ask me)
Less rotating mass to turn, so better acceleration w/AC on
Less cyls, the A6 is a 6 cyl compressor, the R4 is a 4 cyl. As for how much actual flow change, I don't know.

You might find the brackets from a 368 to fit the R4 on the older Cad V8's. But I don't know for sure if the 368's ever got the R4 compressor. You might be able to adapt some Olds brackets from the 307, but they mount it on the passenger side if that is a problem.

Tom

the A4 comperssor was used on all 1980-1984 368 6.0L cad engines
and some 1977-1979 425 7.0L cad powered cars
as well as many chevys, oldsmobiles, buicks , pontiacs ,gmc trucks ,vans and other gm cars and trucks