A/C to OBA

[WrenchMonkey]

Back in August, I had to gut the XJ interior to replace the spring hanger I tore off at Mud Madness. That meant pulling the 12v Viair compressor and 5 gallon HF tank I had rigged up in the back. They worked okay, but the compressor was fairly loud, and the 125psi safety valve had started to blow before the 120psi cutoff switch. So I'd had to knock it down to 105.

I had always intended to convert the AC compressor to OBA, but it never happened. So when a guy from TriState Jeep gave a me a big ole Dewalt tank cheap, I decided it was time to upgrade the whole system rather than reinstall what I had.

[WrenchMonkey]

Years ago, I capped the compressor fittings with 3/4" NPT caps. I seem to remember having to make them fit, but they eventually did. I replaced those with tees (with a ton of teflon tape for insurance) then reduced each leg to 3/8". I considered 1/2", but it really seemed bulky, and 3/8 should still flow triple what my old 1/4 would. (I saw it on the innerweb. Has to be true.)

For the intake side, I got a filter from amazon (p/n UP-104, $12) and an oiler from Harbor Freight (#68233, $11.) The front of the intake tee is just plugged, for an easy access point if I ever have to oil it manually.

On the discharge, I got a 175psi safety blowoff (Viair 92175, $9), and a check valve good for 200psi at 200*. From there, I ran 3/8" copper tube down the firewall. I added a coil (wrapped twice around a coffee can) to hopefully absorb some of the movement of the engine relative to the body. (This is also a decent way to dissipate heat before running rubber hoses, but mine is all metal lines.)

[WrenchMonkey]

Under the Jeep, I wanted something tougher than that thin walled tube, so I used a 3/8 x 6" pipe nipple and a 45. I ran 3/8 pipe from there back to a convenienly placed rust hole in the floor. The first tee feeds a 1/4 line up to a pressure gauge in the console. The second is a 3/8 line to the tank.

A ubolt and simple bracket affix it to the floor. A similar one holds it to the transmission crossmember. No pic, sorry.

[WrenchMonkey]

In the back, my second-hand Dewalt tank squeezes perfectly between the bulkhead and my axleshaft crate, and it's held down with a ratchet strap to eye bolts in the floor.

The air line (all 3/8 copper) comes up from below the floor, tees off to the top of the tank, and over to a Harbor Freight hose reel. P/N 69266, 25ft, $60. I considered the 50 footer, but weight was already a consideration, and 25 is plenty to reach the whole XJ and anybody I'm parked next to.

On the front of the tank (doesn't show in the pic, sorry) is another 3/8 tee. One leg accepts the tubing, the other has a 120-150psi switch (amazon, IS-368, $11) to signal the clutch on the compressor. On top of the tank is another 175 safety. The bottom is just plugged for now, I need to plumb a valve and drain line.

[WrenchMonkey]

The electrical is pretty simple. 12 volts from the battery (Edit: This was a mistake! See update...) through a 5A fuse, to a toggle switch in the console, to the pressure switch on the tank, back to the clutch on the compressor. It grounds through the body.

I've done a couple test cycles. It takes a few minutes at idle to get the 16 gallon tank from 0-150psi, but the output obviously varies directly with rpm. Just moving it around the driveway seemed to cut the fill time in half.

I haven't actually used it yet. I've got an old craftsman impact that I'd like to be able to use on the trail. I think it'll be enough air, but I don't know how good the gun itself is. We'll see.

Either way, it should air up a tire like nobody's business!

[WrenchMonkey]

What's next? On board flux-core welder?

Actually, my good friend Nick Lambert (CopperTop on here) runs one on his XJ. I think he mounted a second, high-output alternator where the A/C was.

It is handy, he actually saved my bacon once, sticking a tie rod back together. But if I only have room for one or the other, I think the air is more useful. Especially if the impact works out.

I guess you can also do it with a second battery? But I don't have room for that either, plus it's another 50 or 60 pounds of dead weight...

[donaldcon]

I convert all my junk to air. I've ran stock compressors from trackers, cherokeea, and toyotas. I usually run 10 gallon tank but have been able.tonuse impact, just gotta let it play catch up a good bit.

There is a lincoln ready welder somewhere in our group. Never carried a spare battery just hooked it to a running jeep and started welding.

[Runoveru2]

I put the factory toyota A/C compressor back in 2004 and have used and abused it, pressure switch kicks compressor on at 110 and turns it off at 150, it has saved my butt and others over the years. I just put a little compressor oil in it a few times a year and it's good to go. With the tank and components I believe I have less than $100.00 in it.

[WrenchMonkey]

Update, the whole system seems to bleed off almost exactly 1psi per hour. I am totally okay with that.

I'm gonna blame the HF hose reel. I could put a block valve before it to verify, and if it gets worse I might. But running the compressor 2-3 minutes every 2-3 days is perfectly fine with me...

[WrenchMonkey]

Update II

Used the hell out of it on the Tour this weekend. Worked great. Will fill a tire in no time, and will definitely run my impact.

One slight snafu: Wiring it off the battery was a mistake. If I shut off the engine before the tank has pumped up, the solenoid on the clutch stays energized. This will (did!) drain the battery in just a couple hours.

I'll rewire it through an ignition switched source, and it should be good to go.

Otherwise, I'm happy as a clam.

[jeepmanjeff]

I installed a Dual Viar system on my jeep. I love it and it works great!.

[WrenchMonkey]

I had a little viair, but it was awful loud, and wouldn't even keep up filling tires at the end of the day.

At 2000 rpm, this one will flow 8cfm at 150psi.