By Steve Delanty

Anyone who owns a shop air compressor knows what a convenience it is.  Filling tires, running air tools, cleaning and drying parts, etc, a compressor is almost a must for any serious gearhead ! But whadda Ya do when You want compressed air out on the road?  Well, You just plug Your air hose into one of the air fitting that's dangling under Your front  or rear bumper of course! When I decided I wanted an on-board air compressor for my '71 F100

 I built a cheap and simple system from an old air conditioning compressor.

Here's how I did mine:

  First thing was to aquire an old air conditioning compressor. One of the most desirable types of compressors to use for on board air  is the old York compressors, which were used on zillions of old Ford (and other) vehicles in the 60's, 70's and 80's. These compressors are an upright 2 cylinder design with a built in oil sump. The oil sump is inportant,  since some compressors have no sump but rather circulate lubricant oil along with the refrigerant to keep the pump lubricated. The only way to lubricate a "sumpless" compressor in an on-board air setup is to use a pre-oiler on the compressor inlet which is not a very desirable way to go.

 Most of the York type compressors have an oil sump to contain the  lubricant oil, so they need no external oiler to keep them healthy. The York pumps have a model # tag bolted to the cylinder head, and may have a number something like this:  F2 10R 16909 The center group: "10R" is the important group to look for.

 You may find 3 models of this compressor which all look similar: "6R", "8R", and "10R". The "10R" is the most desirable since the larger numbers have longer strokes and so move more air. If You find an "L" instead of an "R" after the number, don't worry it means that the air outlet is on the left side of the pump instead of the right side... Once I had the pump in hand, the next thing was to find a mounting bracket and crankshaft pulley for the pump. That was easy, since the York A/C pump was used as stock equipment on almost all the older A/C equipped Ford cars and trucks. I found an A/C equipped, FE390 powered truck at the wreckers and grabbed the mounting bracket and 3-groove crank pulley from it. Everything bolted right up to my motor in a matter of minutes...

Here's a photo of it installed:
 
When used as an A/C pump, the compressors are lubricated by a mineral oil based lubricant. There is no conveniant way to check / fill / change the oil onmost of the York pumps without removing the sump pan.

If Your pump is full of oil when You get it, and You only intend to use the compressor occasionally, the mineral oil lube will probably be fine for years. I intend to use my pump a lot, so I modified mine a little... I removed the sump plate and head and thoroughly drained and cleaned all the mineral oil based lube out of mine. Then I drilled and tapped a hole for an 1/8" pipe plug as close to the bottom of the compressor sump as possible. That's my drain plug...   Then I drilled and tapped a hole a little higher up the crankcase, about where the oil level should be when full. That's my oil level check hole.  I also drilled and tapped a hole near the top  of the crankcase and screwed a pipe elbow into it so the elbow points up. Then I screwed a 1/8"" to 1/4" adapter onto the elbow and screwed a short length of 1/4" pipe into it with a pipe cap on the top. The cap has a 1/8" hole drilled in it. The 1/4' upright pipe has a wad of fine mesh stainless steel screen stuffed into it to catch oil. This little assembly forms an external crankcase vent, which reduces the amount of oil carried thru the pump and expelled into the compressed air, since in stock form the pump vents the crankcase to the pump air inlet... When i was done the pump looked like this:

   

After the pump was drained and mofified, I refilled it with a straight 20W non-detergent oil. I feel better knowing I can check and add oil to my pump once in a while...   Once the pump was set up and mounted, I needed an inlet air filter. I made a filter assembly from a plastic electrical box, a chunk of air filter foam rubber, and some screen. It's not the most elegant setup, but it's what I had laying around in the garage...  

The outlet air from the pump is plumbed into a manifold that splits off to a pressure switch, a pressure relief valve, an air pressure gauge, and two air lines, one that goes to a quick disconnect under the front bumper and one that goes to the rear of the truck. The one to the rear splits under the bed, and one hose goes to a portable air tank in the bed, and one goes to a quick disconnect under the rear bumper.  You MUST use a pressure relief valve!! The York compressors can easily produce pressures well in excess of 200 PSI, and can burst Your air tank! The pressure relief valve should be rated for a pressure equal to or lower than the rating of Your air tank. Mine is rated at 150PSI. An air tank that explodes can send You or someone else to the hospital or the morgue, so please be carefull, O.K.?  

Once the air plumbing was done, the last bit was to hook up the wiring. Power comes from the igntition switch, so the pump clutch can only be energized when the key is on. Power then goes to 10 amp fuse, an "air on/off" switch on the dash, then to the pressure switch, then to the compressor clutch. When the engine is running and the power switch is on, the compressor will fill the tank to about 115PSI then shut off. It comes back on when pressure drops below about 105PSI.  

I managed to scavange used/surplus parts for almost all of my system and ended up with a $$ investment of under $70.  I use it to run air tools, adjust tire pressures, fill air matresses and inner tubes at the lake, and much more! Now that I've got on board air, I dunno how I ever did without it!   (-:

  Happy motoring!