Good video here:
Many more also on youtube.
BTW, an inexpensive digital voltmeter (or multimeter) is a basic tool for any electrical system testing or diagnosis.
Originally Posted by neal
I thought that at least a light would work with truck running. My 2003 dodge has a 12 hot wire in the main plug for aux. batt. on a trailer. Does that wire go directly to the camper batt. ?
Is there a wiring diagram available for the crusader 270RET?
Follow the wiring from the truck. Test the truck battery voltage with the engine running. As you follow the wiring, you should be within a few tenths of a volt that is showing at the truck battery. If you find a sudden drop at some point, you have found the problem area.