So I just picked up that had been on a military vehicle for 200$. There is no visible sign of dmg just dusty. How durable are these things? I don't have a harness to hook it up but he was a old friend of my wife's and assured me the last time it was hooked up it was running fine.

 

Had one in for a couple years now. It runs every time I start the Jeep because I run an air horn. It will air my motor coach tires up to 110PSI when needed. It airs up my Jeep tires almost as fast as a shop compressor. Seems pretty bullet proof so far.

I did have one problem. A heat sensor failed in one compressor. ARB sent a replacement sensor ahead to Moab for me. I picked it up and fixed it in a parking lot. Meanwhile I could still use the other half of the compressor.

 

I had a twin head ARB compressor in my previous JKU Sport, installed at the rear. It supplied pressure for air springs, inflating tires and air tools.
In the current JKUR, I have the same twin ARB but in its portable configuration, for inflating and air tools.
Both have been functioning as expected, no problems.