A/C compressor question.

[56pan]

The R4 a/c compressor on my '93 C2500, 6.5 TD is making end of life rattles so I'm going to replace it with the later style. My son and I just put a fresh reman. a/c compressor on his 2000 K3500 5.7 liter gasser due to the old compressor having a flange leak. His truck cools much better than mine with the later style compressor. I've found that Vintage Air https://www.vintageair.com/ has an R4 to later style compressor conversion bracket that uses a Sanden 508 compressor. Going to milk my R4 through the summer as I'll have to get lines fabricated to fit the Sanden 508. Here's what has me confused: The direct replacement Sanden compressor for a 2000 K3500 like my son's truck is model no. 4440. The 4440 specs are 155 cc. volume per revolution. The Sanden 508 is 138 cc. per revolution. But the R4 specs that I found are 10 cu. in. per revolution which is about
164 cc.? I can only guess that the R4 is much less efficient than the newer style? The Sanden 4440 type obviously cools a GMT400 much better than an R4 with less displacement. Am I missing something here?

Yes, my cooling stack is clean and the truck didn't cool anywhere near as well as my son's truck when the present R4 was new.

[spongebob]

I dont have an answer but I do have a question, why not stick to the R4?, also if you plan on keeping your truck
for the long haul, get a new compressor not a rebuild. reman's dont last very long.

just sayin...

[56pan]

No, raised the hood on my '93 after I drove my son's 2000 GMT400 with the new compressor and had a heart to heart with the R4. "You just ain't cutting it girl. I've found somebody else." I want my truck to cool like my son's does and will get the rest of the life out of the R4 and then she's got to go. Both trucks are standard cab by the way.

[DmaxMaverick]

What refrigerant is in the 93? What was it originally designed for? The R12 --> 134a transition was 1992-1995. If originally R12, then converted to R134a, it will never be up to the later models designed for R134a. If originally R134a, again, it will never be up to the later models, as early R134a systems were much less efficient than just a few years later. Compressor efficiency is essentially limited to how much power they require to turn. Outside of that, if they're meeting pressure requirements, there's nothing to improve, as far as cooling goes. Add to that, the ducting and control changes (1995) really made a difference in the feel, but I think this was a necessary upgrade due to complaints of the R134a changes and early system shortcomings. Swapping compressor models may make the system more (or less) efficient, in some ways, but it won't make the air at the vents any cooler.

[Robyn]

Maverick is spot on...

I have done a fair amount of AC work over the years .....The R12 systems cooled very well....
The early 134A .....Marginal at best.

There are several "Replacement" refrigerants on the market that work well in an R12 system.

I have used envirosafe,,,,,,It has a very close PT to R12


Once you decide to fix your system.....Replace the accumulator, orifice tube and the filter (If separate )

Flush the evaporator and the condenser to get all the old oil and any crud out......

Make sure that you get a compressor that uses an oil that is compatible with whatever refrigerant you are using.....

Add the required amount of oil and Refrigerant......Good to go.....

Some of the replacement refrigerants use different amounts than the original R12 spec.....


The R4 compressor is not a bad unit.....But once they start making noise....They are toast and they will contaminate the system BIG TIME.....Hence the need to flush things out good

[56pan]

Yeah, I imagine the R4 will likely grenade on me and I'll have to flush everything. Would have done that anyhow with a new/different compressor. I changed it to R134 many years ago and put on the R134 spec'd condensor. Evaporator got a pinhole a few years ago and replaced that and that was the job from hell. Had a sideline business in Saudi Arabia from '78-'82 working on car a/c when I worked over there. Plenty of customers in that climate and I understand how car a/c works. When/if I do the change to the Sanden 508, I'll update the thread.

[spongebob]

on a side note you can still find R-12..it's not illegal to own or buy.
the russians still make it.

[Yukon6.2]

Ahhh Those Russians...
There is a group of guys that operate their tow/haul trucks after dark here...
They are also Ahhh Those Russians....

[Robyn]

I was hunting for some tools I need earlier today....Ran across 5 one pound cans of R12....

[sctrailrider]

I was hunting for some tools I need earlier today....Ran across 5 one pound cans of R12....
Want to sell them?

[JohnC]

I was hunting for some tools I need earlier today....Ran across 5 one pound cans of R12....

Just received an ad from a parts supplier I used to buy from. 30 pound cylinder of R12 for only $4,367.47. (That's $145.58/lb...)

[56pan]

Just received an ad from a parts supplier I used to buy from. 30 pound cylinder of R12 for only $4,367.47. (That's $145.58/lb...)

Damn. Guess I won't be changing back to R12.