so we got this 93 ranger as a tradein at the dealer, i was doign the used car inspection on it, checking out any problems it might have repairs it might need etc, and check this out, if you turn on the headlights it stalls, the battery is fine, the alternator is fine, you could be at WOT and the headlights will stall it every time, you could turn on every other electrical devic ein the car and it will have no effect but the headlights will stall it, now i didnt bother diagnosing the problem because the car had so many other problems that we arent gonna bother fixing it and instead of selling it at the dealership, its going to some crap car auction somewhere, but i oculdnt tihnk of any normally occuring problem that would do this, the car did have alot of aftermarket crap wired up but nothing hooke dup to the headlight circuit that i was aware of, so any ideas?

Headlight or marker light shorted?

other than that Id suggest :

www dot ford-trucks dot com

a short is unlikely, if there was one it would blow the fuse or burn out the wiring before it pulled enough power thru those bitty wires to stall the truck, i'm not gonna go out of my way and registe ron another forum to look into this since I won't even be diagnosing it anyway

Could be a bad ground. Maybe on the EEC and whenthe headlights kick on it raises the 'ground' voltage enought to screw up the EEC and stall.

Just guesses really, but Ford can do some ODD stuff when the grounds start to go.
It could be a simole a miswired relay from all the mod'ed stuff too.