I would have bought one year and half ago over the harbor freight had I known. Curious if the postive lead is also grounded to it's frame. 
If it is then I've been really lucky
I usually set the compressor on the fender across the lip, so the bottom of the frame is touching the fender lip.
Must have been an english engineer who designed yours. We had an old MG that suprised the hell out of me when I found out it had a positive ground.
