Electrical problem..

[Z U L8R]

see if he has any brake lights out, sometimes one of the filaments lays across the other and backfeeds the circuit.

but it sounds like there's a short to ground in the accessory lighting circuit.

you can basically remove the fuse and see which side of the fuse the short is on by seeing which leg has power when it really shouldn't have power going to it, then you'll be able to determine which harness has the short in it. either from the accessory relay to the fuse side of the harness, or from the fuse to the component side of the harness....

i use deductive reasoning to diagnose electrical problems. i remove the possibilities of what it can be, then when there's only 1 or 2 things it can be, investigate/test those things for their integrity/correct operation. when you find the "this shouldn't be getting power to it when the key's off etc etc" you're getting close to the problem. that's what i mean by tracing down the short.

to keep it simple...look for burnt wires touching grounded metal objects/other wires
gl,
Dave