PITA electrical

My son has a 2000ES that runs fine except that the rear running lights and dash lights keep blowing fuses( 15amp fuse in the # 15 slot in fuse box in dash next to drivers door) If I replace fuse and turn lights on(without the key in the ignition) they work fine. But as soon as I turn the ignition on the fuse blows. It's OK to drive the car during the day but without rear lights at night it's not safe. Any ideas???? He just started college so he can't afford to bring it to the dealer because we all know how that will end( and I thought college was expense). Any help would be greatly appreciated.


THANKS "BEMAN"

i had something like the same proiblem, when id turn the lights or AC on, itd start my wipers going and my dash would go out. for me, i found out it was a short across the washer motor wiring, itd send a back-voltage, that'd set my wiper going...
it was a pain to get it figured out, and well, if you dont mind wiring stuff up yourself, why dont you run wires from the fusebox all the way to the back to have it come on when you need it to? sounds like a wire AFTER the fusebox is shorting out, since it blows the fuse.

if you have a DMM checking continuity from the light's 12v+ side to ground would also help..

i dont know why it would blow when the ign is only OFF, but it might be due to the amount of current available.. engine on = more current = faster blow?