I got bored over the weekend and decided to turn my portable compressor into an on board air setup. It's a tankless setup, but I figured it'll be easier to air up on the trail by simply flipping a switch and plugging the hose in. The compressor I have is the Harbor Freight one that typically goes on sale for $59.99. As far as cheap compressors go, this is right in line with the rest of them. It's a little bigger than the MV50 that a lot of people get (the little red one from Pep Boys, Amazon, etc) and I certainly don't expect it to last forever, but it airs my 32" tires up plenty quick and I've been pretty happy with it.
I needed a location to mount it - somewhere that it could get enough air to cool off, but also where it wouldn't be completely exposed to a ton of moisture. I ended up deciding on the space where the horns are mounted - behind the driver's side headlight between the back of the headlight housing and the stock air box. The compressor fits into this area well but requires removal of the headlight or airbox (or both) in order to be installed. I relocated the horns to the space between the airbox and driver's side fender (just below the inlet pipe for the stock airbox) and screwed the compressor baseplate down using self tapping screws. Two of the screws popped down into the fender well a little bit, but they were easily trimmed off.
My original plan was to mount a male air fitting to the rear bumper and allow the air to simply flow out of the fitting when the compressor is turned on but not connected to anything. I quickly realized that this would require an "always open" type of tire inflator, which is both hard to find and kind of a pain to deal with.
To remedy that situation, I decided that I need a pressure switch on the system to shut it off as soon as the lines are pressurized. I ordered one online and have yet to receive it in the mail (this is the only thing holding up the finished project at this point). With a pressure switch installed, I changed my design a little to use a female air connection instead, and decided to install one up front in addition to the one at the rear bumper.
I built a small manifold using two "t" adapters. The line from the compressor feeds into one "t", which will have the pressure switch connected to it and the second "t" connected to it as well. The second "t" has an air line running out to the front connection and another running to the back connection. The pressure switch runs to a relay that switches the compressor on and off, and I have the pressure switch wired up to an on/off switch inside the cabin. The pressure switch will shut the compressor off within a few seconds after being switched on, once the lines are pressurized to about 100 PSI. This way, I can turn the compressor on and it will switch itself off as I move from tire to tire, turning back on once I engage the trigger on the tire inflator. Here's a crude drawing of how the system is setup:
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And here are some photos of the install so far. Like I said, I'm really just waiting on the pressure switch to arrive, so I can finish up the wiring and tighten down the clamps on the air lines.
Headlight removed to install the compressor:
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Compressor mounted in it's final location:
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View of the air line running from the compressor to the "t" fittings. I cut the funky chinese fitting end off of the Harbor Freight compressor's air hose and used a barbed 1/4" NPT fitting with a hose clamp in it's place. You can also see the front fitting mounted above the compressor. I used a metal "L" bracket and just screwed it to the back side of the radiator support under the hood. There is a 90* brass fitting under the "L" bracket, and a washer on either end of the bracket helping sandwich it all together:
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A closer view of the "t" fittings and air lines. The black line is coming in from the compressor. The two clearish lines are running out to the front and rear connections on the vehicle. The last open port on the "t" fittings is for the pressure switch (it has a 1/4" to 1/8" reducer bushing installed, as the pressure switch has a 1/8" NPT thread on it):
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A closer view of the front connection, which is mounted above the compressor. In this photo, the airbox is reinstalled, so you can see how everything fits together:
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A view of the "t" fittings with the airbox reinstalled. I plan on using zip ties to simply attach these to some of the existing wire looms in the area, just to keep them from bouncing around and putting unnecessary fatigue on the air lines. I'll attach the lines down in a few places as well, I just need it all loose for now so I can get the pressure switch mounted once it arrives:
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The rear connection mounted on the outside of the bumper. I opted for this spot just to the left of the license plate and kind of high up on the bumper so I won't kick it when I use the hitch as a step:
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A view from the back of the bumper showing the rear air line attaching to the fitting. Just like on the front, I used a 90* elbow to route the line in the correct direction without putting too much stress on it. The 90* fitting has a washer sandwiched between it and the bumper, but there is no washer on the other side of the bumper where the female air connection is. This is because the metal on the bumper was much thicker than the "L" bracket I used up front, and there wasn't much threading poking through to attach the female connector to if I used the second washer:
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Overall, I'm happy with how the system is coming out. The entire setup will have run me about $115 in the end. I spent about $50 on the compressor (used a 20% off coupon when it was already on sale for $59.99), $12 on a 25 foot 1/4" air line which I cut up for the project, about $25 at Lowes on the brass "t" fittings and 90* elbows and 1/4" to 1/8" reducer bushing, $8 on the pressure switch, about $10 for a relay and switch, and a few dollars on the female air fittings, the 1/4" NPT barbed air line fittings and the washers.
