So, I bought the clips that eljefino posted. Didn't take too long and I had the compressor working.
The good: It runs way quicker than it ever has. And I didn't even plug it into a running vehicle - just one of the spare batteries hanging out. I imagine it will be quite quick with 13.5-14V in it. The Jeep has a bunch of 15 year old connections and, even with the engine running, has 11.9-12V at the receptacles.
To test, I inflated a 265-75-16 tire ... much quicker than before and it wasn't getting as hot as it usually does.
The bad: Something got burnt up inside the motor when it was losing voltage due to the Jeep's bad plug. If it stops in a certain position it doesn't like to start up again.
I am headed to the junkyard this weekend for a new outlet panel and alternator. My plan is to find some heavy-ish connectors and make a quick connect system for the other one I bought so I can run it off if a cigarette lighter if needed. But I don't see myself doing that anymore. Picking up an outlet panel for the Focus isn't going to be as easy.
Originally Posted By: dishdude
Those little 12v compressors suck. I bought one of these about 10 years ago, it's perfect for topping off tires and can run on 12v if need be.
I have a few real compressors that run off of 120v. The smallest I can run off of an inverter. This is mainly used for after off roading trips when I need to inflate the tires on the Jeep again or if I'm in a parking lot and come across someone with a flat.