Hi all,

My 12th-Grade Pre-Engineering class and I are renovating a 2013 E450 for our year-long project. The issue that has currently stumped us: there is no power from the two-12 w batteries that is leaving their housing below the chassis. Everything seems fine inside the housing, with proper voltage levels where they should be, but there is zero power below the hood. The truck is outfitted with a passenger side wheelchair lift, which we removed, but there is no power reaching the wires that powered it either.

This is a desperate cry for help.

 

It is likely that the under body batteries were added specifically to power the wheel chair lift. If the three batteries were simply connected together, operating the wheel chair lift with the engine off would draw power equally from all three batteries. If the lift were to be operated enough, the main battery (under the hood) could be drained to the point where it would be unable to start the engine.

To prevent this, there is often a "battery isolator" which disconnects the under body batteries from the main battery when the engine is not running but connects them when the engine is running to allow the alternator to recharge the under body batteries.

You will need to trace the wiring between the under body batteries and the main battery to see if such a device exists. Note that usually only the positive lead is controlled in this manner and all three battery negative terminals are permanently connected to each other (and to chassis ground).

This may not be the cause of "no power at the lift" issue as that circuit should be connected to the under body batteries even with the engine off. While tracing the wires as mentioned above, you may also find some kind of power relay which controls power to the lift. This might be controlled from a switch in the driver's compartment which can be turned off to prevent unauthorized operation of the lift.

 

Is the key in the run position? Everything Ford truck related or originally linked to the trucks electrical system is energized by the ignition switch.

 

My reply to most every electrical question is to supply links to the wiring diagrams. I have no idea where to find the wiring diagrams for your aftermarket equipment. I would get the wheelchair lift manufacturer info off the dataplate and search the internet for installation instructions. This may show the typical wiring methods for this equipment. Send your students on an internet information hunt.

 

My 02
You have a blown fuse link somewhere, or something got disconnected when you removed the wheel chair lift
Start with a 2013 EVTM for the van or the correct wiring schematics for the van you can get at AllData at your library
You will need the power distribution diagrams from the "incomplete vehicle manufacture van" (most likely they started with one of those to upfit)
You mention "there is no power from the two 12 w batteries that is leaving their housing below the chassis"?
Those 2 batteries should just be in a box and the cables attatch to a battery isolator (either switched or automatic)
That isolator needs to be found and checked
Some of that stuff will be hooked up with fuse link wire that will burn the wire inside and leave the insulation / housing intact
Pull on those fuse link wires to check if the inside copper alloy is burnt
If burnt, the wires will stretch like a rubber band
Good luck, have fun in school

 

I have an E350 shuttle bus that originally had an aux battery for running the passenger-area lighting etc. This would have been done similarly to how your wheelchair lift was powered, for the same reasons explained by etinpa and manicmechanic.

The battery isolator in my van is a cylindrical solenoid the size of a small can of tomato paste. It is quite hidden, BELOW the battery tray in the engine compartment. It also, inexplicably, powers the trailer reverse-lights relay - but none of the other trailer relays - which had me really confused about why I had no backup lights! You’ll have to remove the battery and then the tray to even see it without a mirror. These connections are detailed in the “power distribution” set of wiring diagrams, which you will find in the EVTM. If you can’t buy that, I was recently informed on this very forum that your public library may have a subscription to Alldata. There is also Charm (https://charm.li/), which I also recently learned about and have been using. That is free, though the diagrams are quite low-quality scans. It is difficult to navigate… but honestly so are Alldata and Mitchell1, just a little less-so.

Welcome to engineering; it is all about documentation! As you do your work, think about the person who will be coming after you, fixing your messes and repairing your clever solutions. Document the work YOU do so they aren’t stuck guessing at their problems, the way you feel now. Docs are the engineering version of “leave it better than you found it” or “pay it forward”.

 

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