Interesting... the voltmeter that I got at Harbor Freight for $10 has 2 probes...you put the red one on the middle on the power outlet's little middle nipple and the black one on any ground.. Maybe it's proof that there's a lot of difference between rocket science and space cadet? *g*
IF you put a meter on it, I'd be interested to see if the voltage and amps are the same on the 2 outlets when the ignition is on.. As others have said, I'd suspect the voltage drop to be from cheap wires... I ran wires to a 3-outlet setup in the back of the camper shell and it sucked, big time.. I changed the wires that came with it for household 110v cord and they work great... I guess I was expecting drip irrigation size wires to irrigate my whole farm.. *lol*
Mac