Thought about it and my tester isn't what you asked for.......so I drew up one..... It will allow you to plug the tester into a vehicle with a 4,5,6 or 7 pin connector, and the LEDs (could be swapped out for lights) will let you know if the vehicle is providing juice to all the circuits. Leaving the box connected to the vehicle and then plugging the trailer into the box will allow you trouble shoot the trailer while verifing the vehicle is providing juice.
Hooking the alligator clips (I'd use jumper cables) to a 12v source and Gnd, will allow you to trouble shoot the trailer without the vehicle and the LEDs will verify there is pwr going down the line etc....
Under no circumstances should you hook the alligator clips up while the box is hooked to the vehicle...... or you might invent smoke
hmmmmmmm....... I think I'm going to scrap my old one
Last edited by EOD Guy; 12-30-2011 at 08:04 AM.