A/C compressor for on-board compressed air

Aussie company who makes A/C compressors for onboard air

I wanna do this for my truck. But I don't want to spend $1200aus to do it. I figure I can make it happen with some smarts right here in Pennsyltucky.

I already have a CO2 tank (beverage style) at about 4 gallons which was originally rated for big PSI, so here is the basic thought process: Hook up an A/C compressor to supply the tank. sensors to energize the clutch on at 125psi, off at 275 psi - could probably use hi/lo sensors from some junkyard A/C system. Out of the tank to a 125 psi regulator teed off to a connector on the right side and left side of the truck, and teed off to an adjustable regulator for future rear axle air bags. 275 psi and 4 gallons is effectively about the same cubic feet as 135 psi at 8 gallons which should be enough to do most things like air up a tire, use an impact to change a tire, or use an air-over-hydraulic jack.

1- will an A/C compressor be happy starting up at 125psi of head pressure or do I need a blow off valve of some sort?
2- how do I keep the lube in the compressor and not shoot it all to the tank in the first 5 minutes?
3- any other things you can think of?

Try searching some Mini truck sites, I can't remember the specifics, but I remember seeing a few guys who converted AC compressors for their airbag setups.

From memory, there's a particular York unit that works well. I believe it involves stripping the compressor and changing some seals and adding a bunch of grease.

Otherwise, good quality electric compressors aren't terrible value. Viair would definitely have a product that would get the job done.

I know the ancient York twin piston compressors would work, at least for a while, in that configuration. I'm not confident in the 275psi portion of your math, though. Might work, but an unloader would not be the worst idea in the world.

Lube used to stay in the York nicely, but its got a crankshaft and connecting rods swinging around in a sump. I doubt a modern rotary would either need as much oil, or keep it there.

The above is mostly wild conjecture.

AC compressors are lubed by oil in the refrigerant. I don't think it would last long without it. You may be better off using a actual truck air compressor. Other than that, I like it.

Edit: Never mind, those things are expensive.

What you want is a York compressor, often found on old Mopars and AMCs, they have an oil reservoir and don't have to have oil in the suction or charge line to stay lubed.

Seek out the off road/Jeep forums. Search for "York compressor on board air." There's various styles, and some are better than others.

Viair and similar companies make some decent 100% duty cycle 12 volt compressors for relatively cheap though, most of the offroad community has gone to modern 12V compressors and/or pre-charged CO2 tanks for on board air. I know a few folks that still use Yorks though.

The compressor endless air use looks like a reworked sanden, if that helps.

I think you'll struggle to get to your desired psi, engine driven or electric. You'd be better of with a larger tank running lower psi. Higer psi means more resistance, more heat and as such, that'll leed to accelerated wear

An electric compressor and a smallish tank can do what you want. The pressure you're aiming for is a bit crazy though. Most 12v systems max out at about half that much.

We used to have a York compressor mounted on a tractor to provide air for a small sprayer used in test plots. It worked fine for our purposes.

The old York I posted above, I have seen on Fords, Volvo, Mercedes, Porsche, AMC, and in pretty much every aftermarket AC unit installed before about 1980. Any wrecking yard with old European cars will have a stack of them. Volvo used them on the 4 cylinder cars until 1984 or so.

A Chrysler V twin compressor as used up to, what, 1985 or so, would work fine too, I bet.

Toyman01 wrote: AC compressors are lubed by oil in the refrigerant. I don't think it would last long without it. You may be better off using a actual truck air compressor. Other than that, I like it. Edit: Never mind, those things are expensive.

And MASSIVE. They also peak at about 140 psi... which is not the end of the world, I would just have to find a way to hide a 10 gallon tank instead of the one I already have to get enough capacity.

Many off-roaders who do A/C compressors just pack them with grease. That keeps most of the lube in the compressor. I was thinking also about something like an A6 compressor since it has a sump. If I did something like:

daeman wrote: The compressor endless air use looks like a reworked sanden, if that helps. I think you'll struggle to get to your desired psi, engine driven or electric. You'd be better of with a larger tank running lower psi. Higer psi means more resistance, more heat and as such, that'll leed to accelerated wear

Good to know about wear and heat. My thought was that an A/C compressor sees 275 psi every few minutes when operating an air conditioner and they last for 20 years, but its possible in this application (not a sealed, dry system) they might not do so well.

They are Sanden pumps. I think they use the 508 for the smaller ones and the 710 and 814 for the larger systems.

You will not need a large tank. I have been around the old yorks and a few revs on the motor will have it up to 125psi on a 4 gal tank in no time. They really are impressive on how much air they move. It is not at all like a small electric compressor.

GameboyRMH wrote: An electric compressor and a smallish tank can do what you want. The pressure you're aiming for is a bit crazy though. Most 12v systems max out at about half that much.

The pressure goals were originally reached because A) A/C compressors can pretty easily make 300, and B) the tank is rated for something ridiculous like 850 psi. Higher PSI is just a way to get more air in a smaller space. I can use a larger tank and a lower PSI, it just doesn't take advantage of some parts I already have laying around.

former520 wrote: You will not need a large tank. I have been around the old yorks and a few revs on the motor will have it up to 125psi on a 4 gal tank in no time. They really are impressive on how much air they move. It is not at all like a small electric compressor.

I agree, but buying a York compressor is not cheap, nor is it a small unit that easily fits anywhere in the engine bay.

And, yeah... I've done electric compressors before. The cost-to-performance ratio is abysmal and alternators aren't cheap. Even the best electrics move about half the CFM of a Sanden 508

Mercedes 220D's ran those Yorks. And took about 15-20% of the motor's total output to do it. Yeah, they are large. I had a Sanden 508 on the Esprit. You can get one of those new pretty reasonable if you hit the right Texas based automotive AC parts internet store.

I've built a couple of onboard air systems. One for my old bronco and another for an air over hydraulic clutch actuator. The york works well since it has it's own oil lubrication instead of relying on the refrigerant for lubrication like newer systems. They are heavy beasts and getting a little scarce, but a few still out there. Lots of a/c 911 owners ditched theirs. They came in a few mid 70s barges as well. You can also modify a sanden 5 series like the aussie rig (plenty of those - they came in a lot of jeep cherokees - so did sanden 7 series - but the 5 works better for oba conversion). I grabbed a 5 series out of a jeep comanche truck at a pick n pull for $30. Just have to plug a hole, reseal - put on a zerk fitting and fill with synthetic grease. You do have to check the grease every so often and have a good separator. Just sold mine a little while ago. I may still have a seal kit or two laying around. The sandens can crank out around 300 psi. here's a good write-up. There are also the 12v viare compressors that are good to 150 psi. I have an ebay knockoff of one of those (about $100 instead of the $500 viare). Not to be confused with the crappy 12v compressors that take an hour to fill a car tire to 32 psi. It's an oilless thing, so loud - needs about 30 amps, but would work fine too. For wiring, you need a pressure sensor to send a signal to kick the compressor on - whether it's the a/c clutch or the 12v and a pressure regulator. I just had a low amp paddle switch to turn the system on and used a 30 amp relay for the clutch/12v to handle the power surge when the pressure switch triggered the compressor. Oh, in the write-up it says use a 5mm plug to seal the lubrication hole. 5mm is too small 7/32 is better or go to 6mm or berk it and jb weld the hole.

Come to think of it, I had an audi gt coupe with a york compressor - so mid 80s audi 5000s would be another source - probably mid 80s mercs too.

Oldtin... thanks for the link and the ideas for finding a York.

Is the York A/C compressor the same basic unit used in OBA systems?

Yep. Partly why they're scarce. That's the off-roaders first choice for oba. Don't underestimate the sander though. It puts out more air, is lighter and cheaper. You can burn up several for the cost of a york

If you want a York compressor, I have one you can have for free. It came out of my '73 Volvo and won't go back in (will get replaced with a Sanden) when the car is rebuilt. I'm about >< close to putting it to the curb for the scrappers.

When do you want/need it? I'll be heading out your way at some point to help a friend in York, PA do an engine swap in his Spitfire.

In reply to Ian F:

I think I love you. Free is great. I'll toss in some beverage of your choice.

No rush at all. My work at the theater keeps me stoopid busy, so this is a slow winter/spring project.

Regarding the York compressors, I thought you were all talking about the massive York and Bendix units they put in Class 5-8 trucks for air brakes. Those things are 100+ lbs and about the size of an Briggs and Stratton.

I see now you are talking about the smaller ones. Whew.

I like the idea of the extra cfm of the Sanden, but if a York will do the trick without having to continually pack it with grease, I'm in.

I did this on my old toyota. However I dont think you need to worry about high pressure so much, mine put out a ton of volume. It was a stock 85 pickup.

I used an automatic tool oilier on the intake, and a oil/water air separator on the outlet. Worked well. Drain one, fill one, every month or so depending on use.

One thing to watch for, the output is HOT, like melt air hose hot. I ended up using a ~2' piece of hydraulic line as it took the heat much better.

But if you getting a free York that will probably be better.

Wouldn't a purpose built onboard air compressor be easiest? My 2004 Expedition had a unit in the back somewhere, I never messed with it but it seems easy button would be to find one of those in a junkyard.

Streetwiseguy wrote: I know the ancient York twin piston compressors would work, at least for a while, in that configuration. I'm not confident in the 275psi portion of your math, though. Might work, but an unloader would not be the worst idea in the world. Lube used to stay in the York nicely, but its got a crankshaft and connecting rods swinging around in a sump. I doubt a modern rotary would either need as much oil, or keep it there. The above is mostly wild conjecture.

I had this setup on my Jeep many moons ago. It's great because you don't have to pull the oil out of your compressed air, because the lube is never in your compressed air. It is big, that's the only drawback.