My compressor works fine, but won't build sufficient pressure for the rear locker, can't get above 40psi. The ARB unit has been installed for 2yrs but has not been used more than a couple times briefly for very light duty. When I turn the pump on I can smell a strong smell of diff fluid, there is a definite leak. Where do I check? As far as I can tell the tubing from the compressor to the 3rd member is fine. Do I have to pull apart the 3rd??

 

Start by spraying soapy water or some kids bubble solution around to see where the leak is coming from. Maybe you'll get lucky and it will just be a leaky fitting or external air line. If not external, then its internal, which could be a seal or the internal copper air line.

In the future, its a good idea to actuate the locker once every month or 2 to keep the seals lubed up. Although sometimes I've gone 6 or 8 months without using mine. (I try to remember)

 

I second Mt. Goats approach... but fear you may have an internal problem.

My ARB started to smell of diff fluid and seemed to cycle off and on more and more often under use. Then suddenly the compressor just ran and ran and never shut off. Of course, the locker wouldn't engage anymore either.

I removed the diff and bench tested. Air was escaping around the engagement collar. Evidently there are 2 O-rings that reside inside and one or both have failed. Before they let go completely, diff fluid was being forced by them and up the ARB air line... kind of like you have described.

Actually, as bad as all this sounds those particular O-rings are easy to get to, and do not require reseting of your gears. Now, if the leak is deeper inside the unit you are looking at a lot more labor.

My unit is only 6 months old and it failed. I use it a lot, but am bummed. ARB has me under warranty, but have been waiting for well over a week now for the parts. A mailing error or something ARB says. Frustrating.