Page updated: 01/12/2004 10:26 AM

On-Board-Air Using a Sanden Compressor

Instructions on how to design and install an on-board-air system for your vehicle

Written by Al Bsharah

Similar Article: On-Board-Air Using a York Compressor

Why do you want an on-board-air (OBA) system?

	You can run air-tools when you break something on the trail
	You can air-up your tires when you're done wheelin'
	If you have ARB air lockers in your differentials (like me) it provides a reliable source of air-pressure to actuate them

Below is the schematic that I drew (I pretty much stole the design from Matt Osburn) for how the system's all plugged in. My system is geared towards those of you who have ARB air lockers, however, a very similar design can be used for those of you who don't have an air-type locker. Simply remove the section with the ARB solenoids and it'll work just the same. This report covers everything in the diagram except for all air-lines to the left of the first "T" (to the left of the Check Valve.) I haven't installed my nerf-air-tanks yet, but will update this report when complete!

Let's walk through the path of an air molecule, 'eh?

	Ok, you first enter the air filter where you are cleaned of dust and other contaminants. Any kind will do, they can be purchased at many different hardware stores
	Then you're run through a tool-oiler which keeps your compressor running smoothly. It's important you keep the oiler full so as not to hurt the compressor. They even make "air compressor oil" just for this purpose. I think I got my oiler from Grainger.
	The compressor pressurizes the rest of the system by forcing air out the other side. Picked a rotary-style one out of a late-80's Ford Taurus/Sable from a junkyard for about 25 bucks.
	First you'll hit a check-valve (which I eventually decided not to install on my system, I still may at a later time.) A check valve will simply allow air to flow in one direction and isn't totally necessary. I'm told some air compressors need them so that air doesn't leak back into them. Purchased from Grainger.
	Let's follow the "T" connector down towards the Water/Oil trap. This is where all the oil from the compressor and any water from condensation gets filtered out of the air system before going to vital components or out your air line. Purchased from Harbor Freight.
	Next is a pop-off valve which is used in case your compressor system isn't shutting down on it's own like it should. Usually these are set to just above wherever your air system runs at, my pressure switch is set to hold between 85-100 psi (required for the ARB's) so my pop-off valve is set at 125psi. When pressure runs above the value of the pop-off valve, air will be released to avoid massive pressure within your system. Purchased from Grainger, turned out to be a bad one so I had to replace it.
	The ARB solenoids then distribute the air to the differentials, but only when the cab-switch is turned on. When the switch is turned off, pressure is released between the solenoid and the ARB so the locker will release. Purchased from ARB.
	The next item is the pressure switch. Some are variable, some are fixed. Mine is fixed to regulate pressure between 85 and 100 psi. As stated earlier, this is what was required from ARB and is plenty of pressure for me to run basic air tools, etc. Purchased from ARB (one-stop-shopping)
	Next is the quick-connect where you can attach your air hose to. Purchased from Harbor Freight.
	Now, let's go back to the left of the first "T". This portion has not been assembled yet but I will describe it's purpose now and update this page when it is completed. You'll see that the air-tanks are attached with cut-off valves. Cut-off valves are used in case an air-tank is punctured and develops a leak, so I can shut that portion of the system down and still function properly on the trail. Since I have air-lockers, I can't afford to have my air system fail on me!
	As well, I will eventually put an in-cab pressure gauge into the system for visual purposes.

On to the install...

	Here is the parts list <grin>. This is a very tedious project, with an awful lot of small parts that need to be acquired and assembled. Singularly, they're pretty cheap. Cumulatively, they sure add up!
	Here you will see the fittings that attach to the axle-housing for the ARB lockers, in the order they are to be put in. Below is what the assembly looks like completed. The far-right piece goes inside the differential, the second piece is screwed into the differential from the outside. The two small rings are different sizes, so make sure you get them in the right order! The leftmost of the two is the one that fits over the blue air-tube the best, so use that as your test. Be aware that the pieces between the two rings need to be set up exactly the way they're shown. The threaded male-male fitting has a bare spot on one side and that needs to go towards the axle. The rod that goes through it fits best that way. The rest is fairly straight-forward in their diagram.
	This is the air compressor. It's from a late-80's Ford Taurus/Sable vehicle. I chose this because the bolt-holes seemed to be very close to my stock mount, and these vehicles are plentiful in junk-yards where I got the compressor (about $25). Steve McKay fabricated a great mount for it, as you can see. It's incredibly important that your compressor be mounted exactly in-line with your belt-system or you'll go through belts much quicker. This takes some eye-balling and strange measurement techniques...just don't rush this one.
	This is another picture (albeit a crappy one) of the compressor mount that was fabricated.
	Here you can see the air-intake and the tool-oiler going into the input of the compressor. The red hose is simple heater-hose from NAPA. It doesn't hold any pressure, so nothing fancy is required here.
	Ta-daa! Completed system, without any of the wiring harnesses installed. Teflon tape is your friend. Use it HEAVILY! After I got everything connected, including the new belt, pulley, wiring harnesses, switches, I found a number of small leaks. I ended up pulling many sections apart and re-doing them. This is not fun, so do it right the first time! I used my stock jack mount to locate and fix the manifold in place. Zip-ties are as good a friend as teflon tape is!
	Here you can see the air cleaner (blue) coming from the output of the compressor. This goes towards the manifold which is described below. Heavy-duty air-conditioning hose was used for reliability. It's expensive, a bit overkill, but worth it to me.
	Here's the best view of the manifold. Most of the "T" fittings, male-male and other connectors were from Harbor Freight, but you can get them from most Home Depot's and hardware stores for a little more money. Starting from the right you can see the quick-connect, the pop-off valve, the pressure switch, and the front/rear ARB solenoids.

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