I just bought my next baby. A 94 F super Duty with the 7.3 non turbo IDI with just under 150,xxx. Made sure it was the hydraulic dump body and the xlt model. I was in the engine bay the other day playing around and noticed the complete air system that was still there but not being used. It looks like there is a little electric air compressor right behind the auxilary battery ( on the left if your looking in the engine bay) running to a coffee can looking device with a psi meter on the top. The lines coming off of it say air brakes, but why would he convert to air brakes and then back to the disc's which is what is on it now. Any help with why the previous owner had this air setup and what he ran with it would be a great help. I love this thing already, these engines are beasts.

 

It may have been scavenged from another vehicle to make an on-board air setup for tires & tools...

 

or he may have had a fifth wheel trailer with air brakes and used an electric master to control the air brakes on the trailer

 

it was probably for air trailer brakes, or vacume over hydro trailer brakes. my gooseneck had a vac over hydro system on it, i converted it to electric brakes