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ExtremeAire OBA

Another Saturday rolled around and Mike and I got together to finish up his OBA project. 


Here is an updated picture of the compressor and tank.  Mike installed a quick disconnect air coupler for the hose he uses to fill his tires.  You can also see the black 3/8" hose attached to the end of the tank.  It exits the interior of the TJ via an existing rubber plug (now with a .65" hole in it) in the floor of the tub and runs to the engine compartment,  taking the same route as the gas and brake lines do along the side of the frame. 

While the major purpose of this new OBA setup was to provide Mike with a good air up source for his 35" tires, he also wanted it to function as a backup to his ARB compressor for operating his air lockers.  This meant he needed an easy way to switch between air sources, a plug and play kind of solution, while on the trail.  While Mike has not had any problems with his ARB compressor, we both agreed that passing up the opportunity for a backup air supply was just asking for Mr. Murphy to pay a visit on the trail some day.  With that in mind, we worked out a 10 second solution to switch between both air sources.

Both Mike and I had some air manifolds drilled for this project.  I had a pair made from 1" aluminum round stock and Mike had a pair made from rectangular stock.  When we got together, we exchanged manifolds and Mike decided to use the one he brought as it was easier to mount.  Unfortunately, it had been tapped for 3/8" NPT fittings at each end which he hadn't counted on.  (He assumed it was going to be tapped for 1/4".)  No biggie....a spare 3/8" hose barb was put into use and it worked just fine.



The 25' length of 3/8" Goodyear air hose that Mike had was more than long enough to reach from the air tank (in the back of the TJ) to the engine compartment.  He cut off a 2' length and attached a quick disconnect air coupler (the same type that the ARB compressor can be fitted with).  A 3/8" hose barb was screwed into the air manifold and the 2' hose was attached to it.  The air manifold had been constructed with 4 holes drilled through it to facilitate mounting.  The air ports included a pair of 3/8" NPTs that were located at each end, a pair of 1/8" NPTs, and a single 1/4" NPT port. 


A plug was inserted into the 1/4" port (it was intended to be a spare).  The ARB solenoids were removed from the ARB compressor and installed in their new locations, either side of the unused 1/4" port..

It should be noted here that the ARB solenoids do NOT use a common 1/8" NPT fitting but rather a 1/8" BSPT fitting.  The major difference between the two is that one has a thread count of 27 TPI while the other is 28 TPI.  Depending on who you talk to, some say you can put a regular 1/8" NPT into the BSPT tapped hole and there won't be any problems while others say it will leak.  Mike opted to do it the conservative way and purchased a couple of 1/8" NPT to 1/8" BSPT fittings (male to male coupler) from McMaster-Carr's on-line catalog, just to be safe. 

The 3/8" Goodyear hose was secured in the engine compartment with some cable ties and a female air coupler was attached to the end of the hose.  Mike plugged the holes in the ARB compressor with the 1/8" BSPT (you did keep the ones that came in the compressor, right?) plugs.  Since his ARB compressor has the optional tire fill air coupling on it, the hose on the new air manifold will be snapped into this air coupler for normal operation.  If a problem should arise with the ARB compressor, he can simply disco the 2' hose from the ARB compressor and snap it into the Goodyear hose air coupler.  The ExtremeAire compressor and tank will then supply the ARB air lockers with air.  It was for this reason that Mike used an ARB pressure switch to control the ExtremeAire compressor.  The air lockers will never know the difference. 

Once back home, Mike did a quick leak test on the system using the ExtremeAire as the source.  He filled the tank and cycled the air lockers about 10 times.  He then turned the power switch off and waited 20 minutes before turning it back on.  The compressor did not start up which means the tank had NOT leaked down enough for the pressure switch to turn on the compressor.  He had sent me an e-mail with this info and said he was going to check it in an hour or two and to if it the compressor would start.

Well, that is about it.  Like Mike said, this project is DONE!   I hope this has given you some insight in to yet another way by which you can install your own OBA system from pieces and parts.  Good trails and remember to TREAD Lightly! 




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