- Article/photo's courtesy of
- Jeff Holsted
One of the first things some people do before they hit the trails is air down the tires. It's really easy to do, but what about airing back up? There are several options for on-board air on the trails.
York Compressor Install
York Compressor Install
Here are a few options:
* Bring a portable air tank with you. Should be good for a few fills, but won't help if you're gone for a while with no way to air the tank back up.
* Carry a small compressor powered by the lighter jack. It's good for emergencies, but takes a long time to fill a large tire. Some companies sell portable compressors that are made to fill up tires fast, but most won't run air tools, and they are generally over $200.00. But, they are relatively simple to install, and very little if any fabricating will be required.
* Bring a C02 tank. These are much better than the smaller portable air tanks, and will fill lots of tires, and run air tools, but you have to get it filled when it gets empty. And some can cost more than the portable compressors.
* Run a compressor off of the engine. This supplies large amounts of air, is fast enough to run air tools, and will always work as long as the engine is running. The compressor is also fairly inexpensive. But, most likely, a bracket will have to be made to mount the compressor to the engine because there are so many different accessory and belt configurations available for GM vehicles.
Out of all these options, I chose to do an engine driven compressor. The cost, as well as the constant supply of air, were the main benefits. The most common compressor for this type of setup is the York-style compressor. It can be found on Ford, Volvo, AMC, IH, and Oldsmobile vehicles from the late 70's to the early 80's.
Why a York? The compressors found on most vehicles with A/C are lubricated internally, by the freon in the system. For pumping air, you would have to have an external oiler to keep the compressor lubricated, and a filter to remove the oil from the output of the compressor. With a York, this is not necessary. It has it's own internal reservoir for oil, making it a much better choice for pumping air. However, there are many variables when considering which style of York to use. There are three different displacements or strokes available, as well as many different types of hose connections.
Which one do I get? Of the three different stroke models, the long stroke York is the most desirable. The longer the stroke, the bigger volume of air pumped per minute. The easiest way to determine the output or stroke of the compressor is to look at the crankshaft. To get to the crankshaft, you must remove the pulley. This can be done by removing the bolt and washer holding the pulley on, and running a 5/8" coarse thread bolt in to force the pulley off. All models have a flat end on the crankshaft; the edges of the crankshaft are what's important. A beveled edge on the end is the short stroke. If it has a sharp corner, but is grooved for a retaining clip, it's a medium stroke. And if it is a sharp corner without any grooves, it's a long stroke. If the compressor still has the original Motorcraft metal tag bolted to it, you can use that for reference also. It will have a series of five numbers/letters. The last three are the displacement, and direction. Of those last three digits, the last letter is the output direction and the other two are the stroke. The three stroke numbers are: 10 = long stroke, 09 = medium stroke, 07 = short stroke. The Discharge Direction letters are: L = left, R = right. So if it's a **09R, then it's a medium stroke with a right side discharge.
But, the tag is not the best way to identify which model is on the vehicle, because it's common to replace the tag when the compressor is serviced. The tag on my compressor was not the original, and the numbers didn't match any factory output numbers. The single best way to identify the model is to remove the pulley.
Of the vehicles that used York compressors, the long stroke model is most common in late 70's to early 80's Volvos. There is not much information about which models were common on AMC's or Fords, but most people I asked seemed to agree that most Volvos were usually long stroke. I didn't want to spend all day at the junkyard looking for compressors, and just concentrating on finding a Volvo made the search much easier. The hose connectors can also be a factor when looking for the right compressor. Volvo and AMC-style hose connectors, run horizontally across the top of the compressor. Ford-style connectors stick straight up out of the top of the compressor and then connect to the A/C system. This can make the overall height of the unit a little taller. The different connector styles are interchangeable, but finding fittings for the factory A/C connectors is difficult, because the threads don't match common pipe fittings. Fortunately, onboardair.com makes custom flange fittings that use a common 1/2"npt, and they are a direct replacement for the factory fittings. There are also several different types of heads found on the York compressor, but the two most common are the Flange style or the tube "0" or rotolock style.
The compressor I found was out of an 81 Volvo, and had flange style fittings. There are also several different variations of pulley/clutch assemblies found on York compressors. Depending on your particular application, it may be beneficial to get a few different compressors to mix and match the pulleys. New or Used? After deciding on which model to get, I was curious to see how much a new compressor would be. After making a few phone calls, the $200+ I was being quoted was more than the $150 I had budgeted for the whole project, so I decided to get a used one. I made a few calls and the prices ranged from $30 to $75 depending on who pulled it. I picked up my compressor for $35 with a 1-month warranty from the local junkyard. I would highly recommend pulling it yourself. It may be a pain to get out depending on the vehicle, but that will give you an opportunity to grab some of the brackets and the hoses, which you will need later. Before you spend your hard-earned money, you need to test the compressor to see if it works.
There are two things to test for: 1. If the clutch works, and 2. If the compressor pumps air. To test the clutch, look for a single wire coming out of the compressor. This is the wire that is normally connected to the A/C switch on the vehicle, and controls the clutch/pulley assembly. When the wire receives power, it "locks" the clutch, and turns the crankshaft on the compressor. The outer part of the pulley assembly is always turning when the engine is running, and it should spin freely. The inner part of the pulley is what actually makes the compressor turn. To test the clutch, ground the compressor, and touch the single wire to a positive battery terminal. You should hear a "click" when you apply power to the wire. This "click" is the outer part of the pulley, locking to the inner part on the crankshaft. You should be able to turn the pulley with it locked and be able to hear air being pumped. It should also be harder to turn because of this. Also, when you remove the wire, you should hear a "click" again, and the outer part of the pulley should disengage and spin freely again. It is also a good idea to plug one of the hoses with your thumb and turn the crankshaft (inner part of the pulley) with or without the clutch being engaged. Depending on which direction it's turned, it should either suck or blow air against your thumb. It's a good idea to turn it both ways just to be sure it works. If the compressor fails either of these two tests, it has internal damage, or a bad clutch. New clutches aren't cheap, so be sure to get one that works.
How do I mount it? This is probably the hardest part of the whole on-board air project. As of now, there are no brackets mass-produced to mount a York on a Chevy V8. You will have to make one, or find someone to make it. I used part of the original Volvo bracket, and made my own adjustable mounts out of 1/4" steel plate. I wanted to keep the factory A/C for now, so I mounted it right next to my factory compressor. I also had a spare slot on the pulley from the water pump that would allow me to mount the compressor without needing to use an idler pulley to maintain tension on the belt. The compressor MUST be mounted in the vertical position or as close to vertical as possible. If not, the oil will spill out of the reservoir and get in the air lines. If your engine uses serpentine belts, onboardair.com also has a serpentine/v-belt combination pulley for alternators that will allow you to run a v-belt to the compressor. It might work with a Chevy alternator, but I'm not sure.
York compressor installed
Keeping the compressor lubricated. The quickest way to burn up a York is to let it run out of oil. Since it's not pumping freon anymore, you have to keep it oiled. The compressor has an oil fill/check hole on the side about half way up. It has a capacity of about 12 ounces. To measure the oil, I had to come up with a dipstick. You can make your own out of a coat hanger, or buy one from onboardair.com. I made one following Ben Hollingsworths directions on his website: click here. I made sure all of the old oil was drained from the compressor before I hooked it up. This required removing the head, and letting it sit upside down for a few hours.
After cleaning it out, I filled the compressor with 10W-30 motor oil and started hooking up the switch and air lines. Air tank The next step was to find and install an air tank somewhere on the blazer. Having an air tank for storage is essential if you plan on running air tools, and it makes for faster fills on tires. There are a few companies that sell small air tanks that are rated for high pressure (up to 150 psi.) for around $60 or $70. Small air tanks are also common on large trucks that have air brakes. Once again, I tried to save some cash, and decided to look at the salvage yards. I found a 2.5 gallon tank w/brackets at a semi salvage yard for $15 that was rated for 150 psi. and had several 3/8" NPT ports. I put a 140 psi. pop-off valve in the tank and plugged the holes not used. The tank was bolted to the floor of the blazer under the rear seat.
Pressure switch and air fittings. After installing the air tank, the final steps were to build the pressure switch assembly, and mount it to the fender. A pressure switch is necessary to control the compressor. It turns on the compressor when the pressure drops below 90-95psi and turns it off when it reaches 125 psi. This keeps it from running constantly and setting off the safety valve on the tank. I also installed a master switch inside the ash tray to control power to the pressure switch. If the system were to leak down overnight, the pressure switch would turn on, creating an open circuit, if it was wired directly to the battery. It would be possible to just wire the pressure switch to a remote wire, that was on only when the vehicle was on, but I like the extra convenience of being able to turn it on when I want. The pressure switch is a SquareD model #FHG12J52X. It comes with or without an unloader. My local hardware store just happened to have one with an unloader, so that's what I got. The unloader relieves the pressure on the pump when it stops, allowing it to start back up a little easier.
Air tank installed
Air tank installed
The flange fittings for the intake and output ports on theYork came from onboardair.com. Their fittings make setting up the air hoses much easier because the threads are a standard size, and most of the fittings I needed could be found at a local hardware store. For the intake filter, I used an exhaust muffler from Grainger (part #1A328). It's compact and mounts directly to the flange fitting. For the output side I used a braided line from Grainger (part #4HM96) to connect the compressor to the switch assembly. It may be overkill, but the output temperature on a York can get well over 300 degrees if the compressor is run for long periods of time. Temperatures that high will melt most rubber line and the braided line is rated for 500 degrees. The line from the compressor runs into a one way valve, to stop air from coming back into the compressor, when it shuts off.
Then I installed the pressure switch, and hooked the unloader port of the pressure switch to the check valve. After the switch is a pressure gauge rated at 150 psi and then a 1/4" NPT "T" fitting with a quick-disconnect for the air line up front. I then ran a line from the "T" to the tank under the rear seat of my Blazer. I also ran a line to the back of the blazer with another quick-disconnect. Here is a diagram for the whole system.
How it works. Great!! This was one of the cheapest, and biggest bang-for-the-buck modifications I have done to my blazer in a long time. I have around $150 invested in it, and I don't have to spend another dime on it, ever. I decided to run some tests to see how fast it would fill tires and if it could really run air tools. My first test was to air down a 35" BFG MT to 12 psi, then fill it back up to 33psi. The total time on the fill was about 45 seconds. Tank fill time is just under 40 seconds, considerably faster than most portable compressors. The compressor pumps air faster or slower depending on the speed of the engine, and the pulley sizes used. Most of the time, when I'm using it, the Blazer is at idle (700-800 RPM, it's not recommended to run the compressor over 1200-1300 RPM's for a long period of time). I then grabbed my impact and proceeded to remove all eight lugnuts on my front wheel without a hitch, never having to stop to let the compressor fill up. It also can supply enough air to run grinders and ratchets, maybe not as well as a 60 gallon 2 stage compressor, but good enough to make emergency trail repairs.
Would I change anything? If I ever ditch the factory A/C, I will probably make a new bracket, just to get the compressor mounted directly to the motor. I haven't had any problems so far, but I hate to waste the space if I don't plan on running the factory A/C. I also plan on installing a hand throttle to get the engine RPM a little higher when the compressor's running. I have also thought about adding at least one more tank to the system, for just a little more storage. I would highly recommend a York to anyone wanting to add on-board air to their vehicle. It's relatively inexpensive, and definitely trouble free.
Part's used and part numbers:
SquareD pressure switch #: FHG12J52X (125 psi max w/30 psi differential, and unloader) onboardair.com: Flange fittings for York 1/2" NPT onboardair.com
Grainger parts: Filter/muffler 1/2" NPT #: 1A328 Teflon Braided Line 5/16" x 18" (9/16" ends) #: 4HM96 Adapters for teflon line 9/16" x 18 to 3/8" #: 4HM27 grainger.com