Power Winch power supply, how do I check?

[Chesagansett]

I just de-winterized the boat and my less than 2 year old PowerWinch is not working. My setup has worked fine for 2 seasons. I assume it is not getting power. On my setup, I have a fuse at the truck battery (positive terminal); then I have a wire that goes back from the positive batt terminal to a rear bumper plug-in "outlet" The outlet has one of those sping closing plastic doors. The Powerwinch cord plugs into this outlet. Then the cord plugs into the socket at the PowerWinch itself. At some point, something went bad or corroded. I doubt it is the fuse at the battery because if it was the fuse, it would have blown the last time I used it. Everything worked fine up through fall winterization. The cord that goes from the bumper outlet to the powerwinch was stored indoors during the winter. I can't see that being the problem. My guess is that there is probably corrosion at either the plug-in outlet socket on the truck bumper or at the plug-in location at the PowerWinch, both which were outdoors all winter.

Assuming I'm an electrical moron, whuch is pretty close to the truth, how do I go about tracking down the problem? I assume I need a tester (voltmeter or ameter?). There are two cylindrical prongs at the bumper outlet and two cylindrical prongs at the Powerwich. The cord that goes between has a "female" plug at each end that plugs into the aforementioned prongs. What would I set the ameter/voltmeter to, and what leeds get touched to which prongs? In other words, which prong gets touched by the red leed and which gets the black? Does it metter? Step by step, how is this properly tested? For what it's worth, I tried using di-electric tune-up grease to help get a good connection. That didn't work.

Thanks!

Glenn