Which A/C compressor do I have?

Hi all,

Im going to replace my A/C system in my 86 C20 454.

My current compressor is bad, so im going to replace all the major components and switch to R134.

Lookiing on RockAuto theres quite a selection of different pumps. Typically the model number on my current pump is illegible

Can anyone identify it and give me a hint on the correct replacement?

All advice gratefully received, thanks!

Would this be an acceptable replacement, for example?

Yours is a DA6, and the one you're looking at is an A6. It's a better compressor, but it's also much bigger and won't fit your brackets.

The one in the picture looks like an A6, but it’s the strangest set of mounting brackets I’ve seen. An A6 is usually mounted much farther back, parallel to and outside the valve cover, with the front even with the PS pulley. It’s really heavy, so it has multiple brackets.
I think your truck originally had an R4, which is about 1/4 the length of an A6.

You can buy conversion mounts for a more modern Sanden compressor, but then have to adapt the old lines.

So thats one vote for A6 and one vote for DA6 if im reading the above correctly?

kapitein said:

So thats one vote for A6 and one vote for DA6 if im reading the above correctly?

Click to expand...

It depends on whether you want to buy new brackets, but if you are I would personally go back to the r4.

TX87R10 said:

It depends on whether you want to buy new brackets, but if you are I would personally go back to the r4.

Click to expand...

Im gonna do it right and do it once, so these came with an R4 originally? Is that a better pump overall?

kapitein said:

Im gonna do it right and do it once, so these came with an R4 originally? Is that a better pump overall?

Click to expand...

It looks like you are in the Netherlands so I'm assuming part availability and cost factored in to why there is an non stock compressor in your truck currently. If you are able to get back to an original setup and it's known to be appropriately sized personally I would do that. Trying to piece together a new setup to fit a part you inherited will likely be more costly and have more unknowns.

I had to do some more research, but then determined there is an A6 (which my '75 had), a DA6 (used in late 80's), and then a later HR6 (known as the Harrison redesigned model). It seems the OP probably has a DA6.

I don't know if the later models were more reliable than the A6, but it was the A6 that led to the term "Black Death" for a a compressor. It very often broke down inside and released black granules that contaminated the entire system.

I went through a couple A6 compressors with my '75, but the bracket/mounting was a real PIA (big heavy brackets because it was so heavy). I eventually switched to a Sanden (using R134a) and had new lines made by an A/C shop. The first Sanden mounting bracket I got from an online A/C shop in Arizona and it was mostly a single piece of cast aluminum. It worked, but made it hard to get the PS reservoir. I later changed to a set of brackets that are marketed by Vintage Air, but I believe the bracket is really made by Alan Grove.

There is a place in Texas that sells adapters so that you can use your stock A/C hoses with a Sanden, but I've never seen them except online. I think the adapter just bolts onto the Sanden and then has fittings exactly like the original GM compressor.

My '85 K20 has a DA6 and when I swapped the diesel into my '86 Suburban I used the same setup. It worked reliably for as long as I owned the truck. The Suburban had rear A/C too and the DA6 was fine. I believe they switched from the D6 to the DA6 around 1983 or so. One could do a little sluething on RotAuto to see when that was.

The 350 that the truck came with had an R4 doing the same job, so size isn't an issue. By reputation, an A6 is a very robust compressor. I believe the black death was more about mineral oil and old teflon than the design of the compressor.

However, that's all a history exercise. You have a DA6. It's a perfectly serviceable compressor and you already have the brackets. Why reinvent the wheel? But if you are really looking to go big, I'd be considered a Sanden as well.

Thanks for the all the replies folks, so real good info!

Ive read for hours yesterday on various websites and forums, its like going down the rabbit hole there are so many options...!

I think I will try going for a DA6 compressor then. Maybe in the future a vintage air solution is on the cards, but if I can get away with a relatively affordable solution for now, thats what Im going to try.

Thanks!

75gmck25 said:

The one in the picture looks like an A6, but it’s the strangest set of mounting brackets I’ve seen. An A6 is usually mounted much farther back, parallel to and outside the valve cover, with the front even with the PS pulley. It’s really heavy, so it has multiple brackets.
I think your truck originally had an R4, which is about 1/4 the length of an A6.

You can buy conversion mounts for a more modern Sanden compressor, but then have to adapt the old lines.

Click to expand...

IT looks like the HR6/DA6 is much longer than a v5, but the same overall profile otherwise, and the mounting ears may be able to be had in the same distance. if so, id personally convert. The V5 isnt a cycling compressor and it would give you much better mileage for performance and its so much lighter, the brackets wouldnt be stressed holding it , and despite needing to wire the switches, it has one less switch than the Hr6 setups.

also he has an Hr6 guys lol , tag is fortunate to be there

evidently a v5 can fit a r4 bracket with little effort but i have yet to see an example on a carb 350, only a serp bracket set up in gmt400

AuroraGirl said:

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IT looks like the HR6/DA6 is much longer than a v5, but the same overall profile otherwise, and the mounting ears may be able to be had in the same distance. if so, id personally convert. The V5 isnt a cycling compressor and it would give you much better mileage for performance and its so much lighter, the brackets wouldnt be stressed holding it , and despite needing to wire the switches, it has one less switch than the Hr6 setups.

You must be registered for see images attach

also he has an Hr6 guys lol , tag is fortunate to be there

Click to expand...

Ah yeh I see the HR6 now! Thanks !

Last question on this for now, I promise

Does anyone know which belt I will need? On Roackauto it shows the AC belts as being combi-belts that also drive the p/steering and/or fan etc.

As far as I can see I need a belt that goes from the p/steering drive to the a/c....

Again thanks for any input