On-Board Air Compressor Tips

This is a collection of useful comments that people on the various Jeep newsgroups and mailing lists have made about converting York (or similar) air conditioning compressors for use as on-board air compressors.

From: (Jerry Fields)
Date: 19 Dec 1996 14:43:48 GMT

This is a topic that comes up on a fairly often. There are several variations; I used this one.

Took an old York piston-type AC compressor, common on older GM vehicles. It came equipped with 12v clutch. Machined the inlet tube to accept a home-made air filter using a Tecumseh small-engine filter. Modified the output (cut and threaded) to accept standard pipe fittings and equipped it with a quick-connect fitting. So much for the easy part.

This is a big compressor as such things go, and finding room for it under the hood is difficult. I was lucky; my old jeep had a Buick 350 V-8, so the GM brackets bolted right on and I used a stock pulley for power. Rigged a switch to turn on/off the 12v clutch, also installed a pressure switch to cut clutch out at 100 psi and in again at 40psi.

This rig served me for many years. I sold the jeep and bought my Toyota pick up, but there is no room for the compressor under the hood. I now have it attached to an electric motor and use it as a garage compressor, and bought one of those 12v portable compressors to take on trips. it doesn’t work nearly as well, though.

The old York compressors didn’t require lubricant from the freon or other a/c fluids as newer units do. However, the Yorks are much larger and require an upright mounting position, which limits their usefulness in cramped engine compartments. I have seen at least one set up to run from a PTO, and a couple others powered by DC motors mounted in remote locations. If you have a roll cage, some conversions use it as the air tank.

From: (Ted de Castro)
Date: Fri, 20 Dec 1996 14:29:21 GMT

Check out the October 96 issue of 4 Wheel & Off-Road mag. Page 134. The whole process is right there – in great detail!

From: (Jim Bailey)
Date: 16 Jun 97 14:24:31 GMT

Matt Brookins wrote:

I am removing the idler pulley & mounting the compressor right on top of the alternator. It is almost a perfect fit: just a minor home-made bracket. Also, after some measuring this weekend, I don’t have a clearance problem with the hood, even mounted vertical. I will still have 1-2″. I am looking for a six-spline electric-clutch pulley. They came on the ’87-95 YJ’s that had air-cond. Anyone out there

As I recall the York (at least the Mini-York) had a tapered shaft. There are 6 spline clutch/pulleys out there but most don’t fit the tapered shaft. Alternative is to get a 5 spline clutch/pulley for the tapered shaft which is easier to find, remove the pulley, have a machine shop add a spline (did mine for $35) and it was the 5 spline that came with my $20 compressor.

From: buckup@flash.NET (BUD BOREN)
Date: 16 Jun 97 17:48:17 GMT

Daniel S. Hayes wrote:

Hey, one of the list members has a home page that describes/illustrates his installation of an air conditioning compressor as an air compressor. Does anyone have his URL?

On board air—— [no longer active] —

From: (Jim Bailey)
Date: 28 Jul 97 10:00:11 GMT

Ed Cox Writes:

1. Can the York compressor be rebuilt at home in the event it ever fails, and if so how many bananas on the banana scale is the job?
2. I remember hearing that the York compressor oil can be changed. Does anyone know what type of fluid it takes?

I suppose it could be rebuilt but at $20-$30 from a junkyard, why bother? Other than new from the local A/C shops the only other source I know is from Auto Parts Club (the Costco of auto parts). They are on the West Coast and carry rebuilts for about $95.

I use 10w-30w motor oil in mine (last 3 years). If you mounted it vertically, you need to drain the oil down to about 1 inch above the inside bottom of compressor. This prevents oil from being pumped down the air line but still allows plenty for lubrication.

You will notice that there is a threaded mounting hole near the bottom, center on the side of the compressor. This hole is conveniently about an inch above the bottom of the unit. I recommend drilling a small hole through back,center of this mounting hole and with a bolt and nylon washer you have a ready made drain plug.

Using the normal fill hole, just add oil until it starts to run out of the drain hole and plug it up and your oil level will be just right. The above description is valid for a Mini-York not sure about the full size York.

From: (John H. Stewart)
Date: 31 Jul 97 07:46:31 GMT

This is completely unrelated to jeeps, but given all the tampering and tinkering that you guys have done with these in the past few months, I was wondering if anyone knew the maximum pressure that a York compressor can deliver is.

I’ve heard that they are capable of about 150 psi. I’ve never tried it…can’t afford to loose the compressor!

Also, is there any way to passively step up pressure out of a compressor, or can one only regulate down.

You can only regulate down.

Given that this isn’t jeep related, you can just sent any responses directly to me to conserve bandwidth.

Of more concern than pressure is the CFM volume that the compressor will deliver. In order to re-seat tire beads or run air tools, a large steady volume of air is required for best results. The York compressors are rated at over 2.2 CFM. Some tinkering can be done to increase the volume. The Readi-Aire unit is a standard York that has been tweaked to increase the CFM volume. As I recall some specs I saw a couple of years ago, the York pressure output is closer to 200 psi at high RPM.

From: blewey@peak.ORG (Bill Lewey)
Date: 23 May 97 14:29:47 GMT

I seem to remember reading/seeing somewhere that Volvos also used the Yorks at one time. One place said that they were only used until 1981. Correct, or pulling my leg?

I do believe that it is true. When I was looking for a York at my local yards they suggested checking out the Volvos. However as mentioned before, the brackets are almost more valuable than the compressor.

Bill Lewey

From: Kirk.BEasley@trw.COM (Kirk Beasley)
Date: 22 May 97 11:05:20 GMT

I’m beginning to put together plans/parts for the York air compressor on the Jeep. My question, what years were the compressors used? Only on AMC cars or others?…

I’m doing the same too. I went to a local Pick-your-parts and went to the Chrysler section (where AMC cars are placed). The lot had already stripped good core parts (alternators, compressors, radiators, etc) from common cars, but had left the AMCs alone. I grabbed two A/C compressor setups off 258s in case one doesn’t work instead of paying extra for a warranty. I got one set off a ’75 Pacer and the other off a ’77 Coronet (?).

Slight differences though. Both have the York compressor mounted on a bracket up high on the passenger side right below cyl #1 with the alternator mounted beneath it. I haven’t done a detailed comparison of them since they are covered in grease in separate cardboard boxes, but will this weekend.

The ’75 had the York mounted vertical on the bracket and has two belts going to its pulley. One belt goes to the alternator, the other goes to the crank. I think there was one idler pulley.

The ’77 had the York mounted horizontally and only has one belt. The belt goes to the crank and the alternator via two idler pulleys. One idler pulley is mounted to a bracket that uses the two vertical studs by cyl #1 exhaust. The other idler pulley mounts to the timing chain cover by the alternator. This setup requires a different top radiator hose to clear the A/C belt. Don’t remember if the vertical style required a different hose. This car also had a section of pipe to replace the section of lower heater hose which goes from the thermostat cover to just around the valve cover by the compressor. A short section of heater hose went from the thermostat cover to the pipe and a long section from the firewall to the pipe (along side the upper hose).

I’ve seen stock 80 CJs with the horizontal style setup. I’ve also seen one guy install the vertical style without the idlers. Mistake though. His alternator had very little belt contact area and looked very prone to slippage. I will check both styles out before deciding. I want to stay with a stock arrangement so buying belts that fit doesn’t become a nightmare.

Probably doesn’t matter which you get as long as you grab ALL brackets and bolts. Pick-your-parts charge something like $16.95 for the compressor + $ for bolts and brackets. Worked out to be about $40 / setup.

Others on Jeep-L have suggested grabbing the input and output hoses to save $ since finding hoses with the correct York style fittings can supposedly be difficult. Just attach new fittings on the non-compressor side of the hoses. I just cut them off as long as possible and will figure it all out as I go.

HINT: Some AMC cars from the late 70’s have the same horn button setup as pre-80 CJs. The center plastic button says AMC instead of Jeep, but it is a great way to get a very clean button and the contacts. The clear plastic can be pressed out from behind if you really want the same center logo. I only grabbed one for my friend and regret not getting another for myself. One Pacer had the same style steering wheel as the 76-79 CJs and the same style wiper knob too.

From: jslayton@maroon.US.DEll.COM (Jeff Layton)
Date: 22 May 97 16:30:38 GMT

Kirk Beasley wrote:

The 75 had the York mounted vertical on the bracket and has two belts going to its pulley. One belt goes to the alternator, the other goes to the crank. I think there was one idler pulley.

The 77 had the York mounted horizontally and only has one belt. The belt goes to the crank and the alternator via two idler pulleys.

The OEM CJ A/C setup was like the ’77. If you use it for air, mount it vertical, even if you use the OEM CJ belt routing (kinda makes finding replacement parts easier & keeps lots of belt grip on the alternator & compressor – very high torque items) Vertical helps keep oil in the crankcase of the compressor too. Your idea on hoses was a good one – be sure to check output hose temp – freon doesn’t get anywhere as hot as air.

Another upper hose idea is to take the radiator & have a shop flip over the upper hose connector – look closely & you’ll see it’ll gain you about 1.5″ of clearance to the compressor pulley. Cost about $10, $40 to rod out at the same time. See my web page (article 2, I believe – maybe #1) below for a shot of mine installed on my ’85 258. This was before I flipped the compressor vertical (and right before it ate a piston, but that’s another story)

Also, Yorks have 2 style heads – compression mount plumbing (what you have, I think) and flange-mount. Compression mount is A/C specific sizing. Ready-Aire sells adapters to adapt the flange-mount style head to 1/2″ NPT fittings – really slick setup, especially for inlet air filter mounting & plumbing to a whole air system, pressure switch to control the clutch, etc. Harold has the heads available too, or you can find the other type York & swap ’em.

Jeff Layton – Austin (Round Rock), TX

From: (Craig R. Myers)
Date: 23 May 97 07:01:09 GMT

As far as mounting them vertical vs. horizontal, if using for on-board air…mount it vertical! The York compressor has a hole between the “head” area and the crankcase. The reason for this is when used for A/C, the refrigerant oil can get to the crankcase. If mounted horizontally, the oil will run out of the crankcase. BTW, when I built mine, Thorton at Ready Air suggested *any* lubricating oil, ie. 30, 10W30, etc. will work fine. Make a dipstick out of a coat hanger and fill the crankcase with about 1″ of oil. I’ve been using mine for over a year now with NO problems! I have also never had to add oil yet either!

From: (Jon Hylands)
Date: 19 Jun 97 08:35:16 GMT

On Tue, 17 Jun 1997 22:02:33 -0400, “Maurice Cox” ( wrote:

Would there be any problem running a belt from the water pump pulley to the compressor, and one from the compressor to the alternator?

That is how you run it.

If so, how do adjust the tension and would there be any problems with the speed of rotation of the alternator? It would be turning faster, so I don’t imagine there would be.

You need an idler pulley for the water-pump/compressor belt, and the alternator tightens itself below the compressor. The speed of the alternator is not an issue (think of a little high-performance 4-banger cranking out 7500 RPMs…)

See my on-board air page ( for some pictures and a complete write-up on the topic.

From: jslayton@maroon.US.DEll.COM (Jeff Layton)
Date: 23 Jul 97 10:14:06 GMT

Obi-Wan wrote:

All this talk recently of onboard air has got me wondering. I know you can use an ARB’s compressor to fill tires & stuff. However, what if you already have an onboard air compressor & then decide to get an ARB? Do you still have to buy ARB’s compressor, or can you rig up your existing unit to do the job? As I recall, ARB’s compressor setup ain’t cheap.

You can use your existing air with a little work:
1. Regulate pressure down to ARB specs (80 – 105)
2. Rig the electrics accordingly

From: (Jim Bailey)
Date: 24 Jul 97 05:29:58 GMT

This is exactly what I’ve done on my 84 CJ7. I have a mini York compressor and use this supply to run my ARB. I wired/plumbed a pressure cut-off switch on the reserve tank (switch from Currie but available at most valve supply houses) that cuts off the compressor clutch when the pressure gets to 95 psi. I got an electrically actuated air valve from ARB (Yup, the same one they screw into their air compressor) and operate that valve from a switch mounted on the dash. As Jeff suggests you could also use a regulator to step down from a higher pressure if that’s what your system does now.

Why not use the ARB compressor?:

1. Cost

2. CFM is ok to run the ARB but slow to air up tires or use with air tools

3. The ARB is a poor continuous duty compressor (as in airing up your tires and the rest of you buddy’s tires). It’s also a noisy mutha! The ARB air solenoid and lines use a very small volume of air. Under repeated switching the compressor will engage frequently. With only a 1.5 gallon tank, I can switch on/off maybe 30 times before my compressor will engage. I run unlocked as much as possible (more challenging that way) and can usually run all day without the compressor engaging. If you do use ARBs compressor, I would suggest adding extra tank capacity.

4. Several have been just worn out from continuous duty use. One acquaintance carries a separate compressor for tires so he won’t risk losing his ARBs (i.e.-no compressor = no air = no locker).

From: jyokomur@hawaii.EDU (Jeff S. Yokomura)
Date: 26 Jul 97 17:55:08 GMT

I’m trying to decide on what I need to be able to run some air tools from my Jeep. I know a ARB compressor isn’t up to the task but I’d like to go as inexpensive as possible. The average impact wrench is about 2.2cfm @ 90 psi. What will I need the compressor to be rated at to keep the impact wrench happy? I’ve been thinking about using a Quick Air 2 and a 2.5gallon tank but the Quick Air 2 is only rated at 1.27cfm @ 50 psi. Will the tank at 150psi be able to keep the impact wrench going? What other choices do I have? I’ve seen the Ready Air electric but it’s $450. I’d like to stay electric since I need the AC space. I’ve seen a setup using two Quick Air’s running together.

From: lobel@uscom.COM (Larry Lobel)
Date: 28 Jul 97 16:02:46 GMT


If you must save space you can use: a CO2 tank, an old oxygen bottle, a fire extinguisher, or simply an air tank. Walmart sell’s an air tank for 29.95. Home Depot is 24.95, and Caldor or K-mart just had a sale for 20.00. PVC cannot handle the pressure and will fatigue after a 100 cycles or so. Besides, no matter how much PVC you use you won’t have enough volume to knock a bug off your fender. I just installed onboard air using the factory A/C York compressor and a mini regulator. I’ve seen the setup on the web w/o the regulator and using a pop off valve and drain hose, but it is easier to do it this way:


  • York compressor w/ brackets ($10 junkyard)
  • Flare fitting reducer 1/2″ flared F to 3/8″ thread M ($2 H.Depot)
  • 3/8″ M to 3/8″M brass fitting ($2 Home Depot)
  • Mini regulator ($15 Pep Boys, $19 Home Depot)
  • 3/8″ pressure hose w/ 1/4″ fittings 25′ ($15 anywhere)
  • Campbell/Hausfield (sp.) compressor accessory pack ($15 H. Depot)
  • Tank-specific to vehicle. I bought a used air tank from a welder that is a little larger than the current air tanks. It’s 2′ long and 10″ around. It will run an air ratchet for 45 seconds straight when the tank is at 120 PSI. A smaller tank such as a bumper or roll bar won’t let you get a lot of work done w/o refilling breaks.

Other parts include teflon tape, a toggle switch, and in-line fuse. I have a ’78 CJ with factory air so when I took the A/C unit out I plugged right into the fuse block with the toggle switch. The compressor clutch plugs into the harness wire. Future plans include putting the A/C unit back in and running two compressors mounted to each other. I got the dual accessory toggle switch so tools up, A/C down. Sorry for being so verbose. Steve Lobel PS- If you are getting a new, longer belt: buy 5 or 6 the first time out and return the ones that don’t fit. Now I know how Norm felt when he walked into Cheers.

From: jslayton@maroon.US.DEll.COM (Jeff Layton)
Date: 28 Jul 97 11:03:13 GMT

Tim Taylor wrote:

I have a ’77 CJ-5 with a 258. A local junkyard has an ’84 AMC Eagle with stock A/C.

The A/C pump is located where the alternator is on my Jeep, but I could get the brackets for both the A/C pump and the alternator to relocate it on my CJ.

My question is, will this A/C pump work for on-board air?

I used a similar setup on my 258 (pre-blow-up). The only thing you need to watch out for is to get the proper belt arrangement. AMC used about 3 different belt arrangements of the “York-on-258″ setup, including a serpentine arrangement. See one of my Jeep articles (in sig below) for a setup that worked for me – it’s the factory CJ setup, also found on some AMCs.

Basically, beware of one of the setups that uses a thin V-belt for the alternator – I felt it was too little for good torque on a hi-amp alternator. My web page shows the setup before rotating the compressor vertically. Whole setup cost me about $40. Real trick setup is to swap heads on the compressor with the flange-style heads & purchase from Ready-Aire the converters to 1/2” NPT threads – makes it very easy to rig up an air system.

From: chet@velocity.NET (Chet)
Date: 16 Aug 97 19:40:21 GMT

I just bought a 2.5gallon air tank to mount under the hood. I just > have a few questions about the tank. Why are there so many holes in the > thing? I counted 5 and I don’t know how I should plug the other two. I > have the compressor using one hole, the air regulator using another and the > drain plug on the bottom. I don’t have a overflow valve yet and I don’t > know where I should be going to get one. Gonna try hardware stores > tomorrow. This still leaves me with one hole left. How can I cover it? > Stick a bolt into it with some teflon tape?

If you are going to mount this thing under the hood I insist that you install an overflow valve – I know we are only talking a few hundred PSI but when that thing gets hot the pressure is going to take off – in the name of safety you really need the valve – maybe you are like me and think shrapnel tears in your hood would serve as a great campfire story at your next trail ride though – your choice.

If you are looking for the experts on pressurized containers I would flip through your yellow pages and look under “tanks” – there are usually a half a dozen shops within 50 miles that work on all sorts of pressurized tanks – you can also check the local welding shops or gas suppliers – not auto gas but like the industrial welding stuff – you know what I mean – you can also check a local scuba shop – they sell 3000 PSI tanks that require inspections – every five years they have to find a local shop to test the tank above its rated limit – the shop they deal with should be able to help you out.

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