i have a 98 dodge grand caravan sport with an intermittent tail lamp problem.
nope, not a short, not the headlamp switch,40amp fuse and relay ok. seems to be some kind of headlamp controller problem.
the tail lamps work fine in the parking lamp position, but when switched to the headlight on position the tail lamps go out and wont come back on even if you go back to the park lamp position. if you shut the vehicle off then turn the key back on you have tail lamps at the park lamp position on the headlamp switch until you try to go to headlights on position again. i've got over 10 years experience in the auto repair feild and i'm stumped and embarrased. if anyone can help me it would be greatly appreciated.

p.s the vehicle has daytime running lights and a trailer wiring harness which also checked out ok, i also completly dimantled the headlamp switch and cleaned the copper contacts and regreased them.

Hmmmm there has to be a short somewhere. Sounds like one wire is grounding out when you turn the lights on fully. Maybe someone else has another idea, but that's my $.02

Looks like there is a BCM (Body Control Module) on this. The taillights come out of the headlight switch & into the BCM then to the lights. It could be faulty causing the problem.