I am trying to find an electrical problem in the headlights and running lights on a 2016 F450 6.7L ambulance

[Oviedo Dave]

I am new to this site and hope I am posting this in the right Forum. If not please advise where I should be asking this question. First off I am a trained mechanic, but have never come up against the modifications present in an Ambulance, or what may have been done to "de-commission" it, plus I am not a modern DC electrical systems expert as far as SYNC enabled vehicles go. I do have a factory repair manual coming, but have so far met nothing but frustration since no matter what I do the headlights and running lights are on at all times. If the Batteries are connected, the headlights are on as well as the running light. This is with No ignition key, and even after I unplugged both the headlight switch, and the BCM the light stay on. I have not bothered to pull the actual headlight fuse from the main fuse box because that really does not point me anywhere besides a problem with the main circuit, which I can not find any useful information on in the first place. I have pulled every "extra fuse" that are tied in under the steering column that are labeled as connecting the ambulance electrical circuits to the illumination system of the truck. I can not find any information online about relays that are part of the fuse box (the one mounted in the passenger side kick panel), nor any in an engine compartment box, hence the need for the factory repair manual. I have examined the huge circuit panel and found the board, wiring, and twenty or so 5 pole relays that drive the various components of the ambulance box rather daunting, but they seem to be properly identified, and have pulled each and every relay without any effect on the lights.
I suspect a fused relay that is embedded on the fuse box circuit board, since I had a fuse box fuel pump relay fail on an 04 F250 6.0 and it was easily diagnosed but could only be repaired by replacing the whole box.
If anyone on this site has ever run up against any post 2011 F series Ford that has experienced the headlights and running lights being stuck on, and knows what caused it, please reply. I will have the factory manual CD in a few days, but I will be back working on Monday so my time will be limited until next weekend. This may or may not be caused by any modifications done during the ambulance de-commissioning, but I will not simply start swapping parts without some kind of rational explanation of how/why this problem occurred.

Thanks in Advance, Dave in Oviedo

 

[IdaSHO]

Good luck. Ambulances are typically an absolute mess of upfitter wiring. This is also a platform that utilizes CANBUS, so the changes/fixes you need to make may require access to the ECM/BCM. I use ForScan. I do know for certain that headlights/DRL as well as running boards (puddle lights) are both controlled by the ECM/BCM and dont necessarily have their own fuses.

 

[Betarocker]

It might be related to the flashing unit that ambulances have, and if it was removed the wires may have been reconnected incorrectly???

All OEM switching is done through the vehicle's robots, so your problem seems to be between the lamps and the droid.

ForScan allows DRLs to be set from either headlight (50% brightness), turn signal, fog lamp, or off.

 

[Ole Chipper]

Would start at the wiring near head light bulb and backtrack to where it's spliced. Cause someone rewired direct power to those wires.

My old 89 F-350 ambulance I ripped out all the modified wiring. Put it back to stock and added what I wanted to control the inside lights. Off one main power wire. Mine was all wired with red wires, some with numbers most without. Honestly think I saved myself days in labor and frustration.

 

[Pacific Northwest yetti]

Man, Good Luck. When it comes to Ambulance upfitters, or any emergency service upfitters that’s a tough one. Although, ambulances seem to be worse. I have spent uncountable days in medic units.

And by the time a agency decides to Decom one, they have a lot of gremlins. Some good advice posted above. Either way its going to be a lot of tracing circuits, and process of elimination.

Do you know what they pulled out to ‘ De- Commission” it? Most places just pull the badging and leave the rest to the buyer. However, CA has some specific rules on this. So does it still have the light and siren control?
A few up fitters, wired in the headlights, and running lights to be on, anytime power to the box was switched on. Even if the truck was off. Possibly labeled “main,box,rear.body”

As well as they have disconnects specific to the starting battery.