On-Board Air System

Selecting a Compressor
I considered a York piston compressor with it's seperate oil reservoir, but couldn't find one with the serpentine pulley. They are also larger and don't really offer any benefits over the rotaries (see footnote). I found a stock Sankyo rotary compressor from a Jeep and decided that it could easily replace the existing idler pulley. This compressor was off the shelf in a Kansas junk yard so it didn't come with any mounting brackets. The factory mounting brackets require the use of a different belt for the A/C setup. Since I carry a spare serpentine belt and didn't want to replace two relatively expensive belts I made brackets that use the non-A/C belts.

Before you lay out the cash for the compressor connect a battery and make certain the electro-magnetic clutch works. While the clutch is engaged spin the compressor and see if you can feel suction and/or pressure through the ports.

Mounting the Compressor
Sorry, I didn't take any pictures of the brackets, but they are just two pieces of angle iron 1.5 x 2 x 8 inches long. The hardest part was getting the compressor with a 5 inch pully to replace a 4 inch idler and maintain the same belt tension.

Building the Manifold
The main reason for choosing this particular pressure switch was because it has four 1/4" NPT ports and becomes a compact manifold that all the other parts screw into. This switch will start the compressor when the pressure is less than 90 PSI and turn it off at 125 PSI by cycling the magnetic clutch on the A/C compressor.
The parts in the list below came from Grainger equipment and supplies.

Addendum: For some reason (heat, vibration or oil) the polycarbonate bowl has cracked on three different oil separators. I have since discarded them and am looking for a small industrial grade oil separator.
I also replaced the inline check valve with a more positive check valve triggered by the pressure switch instead of the input/output pressure bias. The picture doesn't quite match up to the components now.

Grainger Parts Item P S I Stock # Price Pressure Switch 90-125 5A537 22.93 Safety Valve 150 5A709 5.90 Unloader/Check Valve 150 5X780 9.10 Mini Air Line Filter 150 2Z766 15.55 Pressure Gauge 0-160 1X754 4.10

Other Parts 1/4" NPT Brass Street Elbow 1.89 1/4" NPT 2" Brass Nipple 2.39 Compressor to Manifold Hose 14.95 Manifold to Bumper/Tank Hose 3.00 K&N Air Cleaner 10.00 Air Cleaner Adapter 6.79

Mounting the Manifold
I mounted the manifold to the bulkhead that supports the radiator. There is a rectangular hole behind the headlight with a lip that has to be ground down to 1/8th inch. I used 1/8th inch thick washers behind the angle iron mounting bracket to clear the lip.
The air hose comes out of the bottom of the manifold and goes under the grill to the front bumper.

Electrical
The source of power for the compressor clutch is a wire from the fuse block that is controlled by the ignition switch. If switched power is not used the battery will be drained if the air pressure drops below the pressure switch setting. I've also included a master switch so the compressor can be disabled when not in use. The switch could be mounted under the hood with the manifold, but I chose the dash so the air tank(s) can be filled as I approach the end of a trail.

Comments:
I run my compressor dry most of the time. I initially drained the A/C oil out and poured in some of that miracle oil (Pro Long) advertised on TV. I ran the compressor for a while to make sure it was miracalized and blew all the oil out. Now I just squirt a little Pro Long in the intake every 2 or 3 months and get very little, if any, oil in the air hose. This compressor has been running for over a year this way, but I'm prepared to spend another $25 if it seizes up. YMMV

Grainger also sells Dynaquip quick connects that will accept any of the three different style connectors available (automotive, industrial and ARO 210) for air lines and tools. This way I can use hoses and accessories from anyone I'm traveling with. Part numbers are Dynaquip DW-340, Grainger 6CX02.

I found that 7/8" crutch tips available from the local hardware store are a perfect fit for the quick connect couplers on the air lines. This way you don't have to dig mud and debris out before each use.

After Thoughts
For those of you that prefer the York piston type compressors over the rotaries you can get mounting brackets, serpentine pullys and other accessories for your on-board air system from Kilby Enterprises in Burbank, California.