turn on headlights and engine dies

[devincox]

I found that when I turn on the headlights, the engine dies and the theft light starts blinking. Turn the lights off and the engine will start again. If the lights are on the engine will turn over but never start.

I also noticed that there is a slow drain on the battery if the the light switch is turned on, even when the ignition is turned off.
I have recently added some aftermarket headlights so I thought maybe the wiring of the new headlights was to blame, so I disconnected them but if the headlights are disconnected, the truck will not start at all.
If only the drivers side light is disconnected then the ecu relay switches open and closed rapidly and loudly.

As a side note, I recently replaced the engine and transmission and thought that maybe some of the wires were positioned out of harms way and maybe got on a header or something, but have found nothing.
I have checked all fuses and relays and found nothing yet. I'm stumped at the moment and wondered if anyone has seen this type of thing before.

 

[stamp11127]

How are you at reading a volt meter and wiring diagrams?

 

[devincox]

Ive been looking at the wiring diagrams in my chiltons, and think it has something to do with the RAP (anti-theft) module. It looks like a rats nest. some exposed wires, random looking splices and such. I ran out of daylight and will have to look more into this tomorrow. Thank you for the pdf, its way better than the wiring diagrams that I have.

 

[Bedrck47]

Ive been looking at the wiring diagrams in my chiltons, and think it has something to do with the RAP (anti-theft) module. It looks like a rats nest. some exposed wires, random looking splices and such. I ran out of daylight and will have to look more into this tomorrow. Thank you for the pdf, its way better than the wiring diagrams that I have.

Chilton Haynes and Clymer are only good for starting campfires,

Get yourself a copy of the Ford Service Manual on DVD

http://www.expeditionforum.com/threads/factory-service-manuals.25089/

 

[devincox]

pulled out the aftermarket alarm today looking for the short. It was a mess. Found some water inside the truck too. I think my sunroof is leaking. That will be next on the list of fixes, especially if the water is causing the short.
Now on to the headlight wiring.

 

[docraymund]

Something is using the ground system of the headlight for power. Concentrate on the relay box for short circuit.

 

[devincox]

Finally figured it out. Bad ground on drivers side headlight. The ground on the radiator. Thank you for the help guys.