Onboard Air

Introduction

I am not going to get into why you need to air down on the trail or the benefits of having air tools available on the trail.

Also, I am not going to go into building the entire setup. There are plenty of websites out there that cover the entire setup. The hardest part of one of these setups is getting the A/C compressor mounted. I will show you how I mounted a factory compressor rather than using a York.

First, let me describe my logic behind choosing my onboard air solution. You basically have four ways to go. This was my pro's and con's list. I am sure there are more but these were the ones that stuck out in my mind the most.

Pro's and Con's of different systems

Compressed Gas: A tank that contains mixture of CO2 and Nitrogen.

Pro's:

• Can be easily moved from vehicle to vehicle
• Contains the most pressure. Best for reseating tire beads
• Engines does not need to be running, heck does not even need to be near a vehicle to operate
• Can run air tools
• Can be made or bought
  

Con's:

• Contains a limited amount of gas
• Needs to be filled
• Although gas is inert the pressure can be hazardous
• Not recommended to run air lockers (although some people do)
• Takes up cargo room
• Heaviest solution, depending on size of tank.

Typical Cost: $150 to $400 with mounting hardware.

Electric Compressor: An electric compressor that either runs by being plugged into your cigarette lighter or is permanently mounted and wired to your vehicle.

Pro's:

• Overall a cheap solution
• Engine does not have to be running in most cases, but typically need to be near your vehicle
• Can also run air lockers if you have the under hood versions
  

Con's:

• Slowest of the bunch
• Some compressors cannot run for extended periods of time (over 15 minutes)
• Cheap ones cannot run lockers
• Cannot run air tools at all (in some cases, with a tank you could run it limited bursts)

Typical Cost: $25 to $350

Onboard Air: An A/C compressor that has an air tank and pressure switch connected to it.

Pro's:

• Reseat beads on tires
• Virtually an unlimited amount of air
• Run air tools on the trail
• Can be mounted without taking up cargo area

Con's:

• Has to be made, there are no complete kits for this setup (can be a pro if you enjoy to do stuff yourself).
• Engine must be running in order for system to work
• Cannot be moved from vehicle to vehicle
• You can only go as far as your hose will allow
• Most expensive of the bunch
• May have to purchase or fabricate special brackets
  

Typical Cost: $200 to $600

Mooching off my fellow trail mates

Pro's:

• Cheapest solution
  

Con's:

• Becoming know as the person that mooches on the trail
  

Typical Cost: Your good name

Searching for a solution

For me, it really came down to the Compressed Gas and the Onboard Air.

One of our friends has a compressed gas that he let me use. It works well and is very fast. He has a Jeep YJ, the tank took up a decent amount of cargo room. Also, once he allowed me to use it, 3 other people wanted to use it. He let them, but my only thought was how much more compressed gas could be left. I also did not like the idea of having 2500 psi sitting behind me either.

The hardest part of an onboard setup is getting the A/C compressor mounted. I knew that if I could find a factory A/C unit, it would bolt in. Then all I would have to do is to buy a longer serpentine belt and the hard part would be behind me. The other advantage to having a factory compressor is that I would not have to change out my air filter to an aftermarket one. I started looking at the normal resellers online. A refurbished A/C compressor cost between $230 and $300. I was not willing to pay that much, since I did not know how well it works compared to a York.

I have become an eBay'aholic. I was searching for an A/C compressor on eBay and found one. It was described as: 1995 4.0L Jeep Cherokee A/C compressor 85,000K. It was pulled from a straight six (I have a 4cyl.). The picture that was included with the ad looked like it would bolt up. I bid $41.75 on the item to win it. Also, he charged $12 for shipping. Total cost $53.75. Not bad in my opinion.

Mounting my compressor

I received the A/C compressor that I had won on eBay, about a week later. The compressor matched the mounting bolt pattern of my Jeep. The gentleman that sold it to me also included the bolts and a belt.

Picture of my compressor. Missing manifold. As far as I know this compressor will not fit YJ's.

Next, I check the clutch pulley. I connected the battery and it clicked. I tuned the pulley by hand and you could feel it pumping air. Unfortunately, the belt he sent was too long. I used the long belt and marked the length I would need. I went to Checker auto parts, the salesman measured the belt and gave me the part (Dayco Poly Cog 5060915) serpentine belt. I installed it on my Jeep, it barley fit (I initially thought it was too short).

With the mounting taken care of, next hurtle was to make a manifold for the A/C compressor. The compressor did not include the pressure lines for the manifold to connect them. I took an etching of the area and scanned it into my computer and printed it out. Next, I found a ¼ inch piece of steel that was lying around and tracked the outline of the manifold on it. I used a grinder to cut the piece of steel to the correct shape. Next I marked and drilled the holes for the bolts.

I took my compressor and my new manifold down to Ace Hardware and bought some Grade 5 bolts to mount the manifold (trust me it is easier to take everything down there and make sure it fits at the store rather than to make several trips to get the right bolts). I drilled the manifold for the NPT holes and tapped the holes. I installed the NPT hole ends on the compressor. The compressor is now mounted and ready for the rest of the onboard setup.

Copper is the output side of the compressor. The blue hose is the intake side.

Some things you should keep in mind.

Safety - Pressure relieve valve (mine works at 150 psi). If the system goes above 150 psi then the system will automatically release air.
Pressure Switch - My turns the compressor on at 95 psi and shuts off at 115 psi.
Air intake cleaner - You will want clean air going into your compressor. You do not want to damage the compressor or be filling your tires with dirt. I think a cotton filter, like a K&N filter is best.
Oiling the compressor - I bought an oilier from Harbor Freight for my system. I also poured a teaspoon of oil in the compressor (air intake side) to make sure it has enough oil. Someone suggested I also put a small amount of Slick 50 in there to give it a Teflon coating (I have not done this yet but I am considering it).
Oil and water separator - Mine cracked a few days after I had it. I think it was the heat. I am not using one currently and do not have plans to.
Wiring - Make sure your onboard air system is properly fused.
Switching - My switch is located in the cab. It is a lighted switch. When the system is turned one the switch lights up. When the system is off, the switch is not lighted.
Tank - A tank is nice to have, it give you a reserve of air. I have a small 1 gallon tank on mine.
Hose - You will want something that will be able to withstand the pressure and also withstand the heat of the engine. The compress gets pretty warm, especially after a day of 4x4'in in 90 plus weather. I am using copper tubing for the first 2 ft. or so. This will help disapate some of the heat.

I have a 3 way valve coming out of my tank. One goes to the pressure switch, one goes to the output and the last is the saftey pressure valve (that one is hard to see).

Conclusion

So far I have used my onboard air only for airing up tires. The day after I completed it, I needed to use it. I finished my day at work and walked out to a flat on my Jeep (I had picked up a nail in the tire). I was able to air up in the parking lot in less than a minute. On the trail it has been really handy. I can go from 14psi to 32 psi on my 31x10.5R15 tires in less than a minute. Pretty impressive.