Cabin Power Conversion

[WanderingLex]

Hey there 👋👋

I am just starting my conversion, and well, besides the bed, electric is first!

My bus is a 2009 e350 super duty chassis with a handicap shuttle body (4 windows).

I'm trying to remove all of the stock wiring from the cabin so that I can install a solar system. What I can't figure out is that when I pull out the cabin fuse panel, the engine won't start. Obviously, I'm breaking the circuit somewhere.

Wondering if anyone knows how to bypass the cabin fuses so that I can pull the second battery and get rid of all the extraneous wiring. I figure there's a relay somewhere in the engine bay, but don't know where to start.

Thanks in advance! Wander Safely & Stay Well!

[Rucker]

Not terribly helpful if you've gone and done it already, but I left absolutely everything intact and in place, and built my house electrical completely independent of the chassis electrical.

[Simplicity]

School buses integrate the mechanical body and the bus body electrical so that the bus body electrical safety features affect the mechanical body ability to start.

Trying to dissect the two electrical systems would take a skilled automotive electrical person a long time to assure the bus continued to start and run.

To try to integrate a house system into the mix seems virtually impossible, and probably create more issues than solutions.

I think running your bus body/mechanical, 12v home and 110v home systems separately will give you the most reliable system.

[Danjo]

I left all mine intact as well

Why make it harder?!

[HamSkoolie]

Originally Posted by WanderingLex

Hey there 👋👋

I am just starting my conversion, and well, besides the bed, electric is first!

My bus is a 2009 e350 super duty chassis with a handicap shuttle body (4 windows).

I'm trying to remove all of the stock wiring from the cabin so that I can install a solar system. What I can't figure out is that when I pull out the cabin fuse panel, the engine won't start. Obviously, I'm breaking the circuit somewhere.

Wondering if anyone knows how to bypass the cabin fuses so that I can pull the second battery and get rid of all the extraneous wiring. I figure there's a relay somewhere in the engine bay, but don't know where to start.

Thanks in advance! Wander Safely & Stay Well!

When you say you pulled "the cabin fuse panel" do you mean the panel for the BUS BODY?



I used to work on E350 SuperDuty vans with transit fiberglass 19 pax bodies.

Our buses had the standard chassis (CABin) fuse block and then a "bus board" with a circuit board, fuses, relays, and some chips. Our buses had them in the overhead at the front of the bus but that's going to be dependent upon the builder.

If ANY of these circuits were broken or the board removed, the vehicle was inoperable.

I suspect you mean that you're pulling the bus body panel and what's happening is you're interrupting a starter enable circuit.
Your rig is largely just a Ford E350 and you should be able to find the schematics via Ford, a GOOD repair manual (the Ford service manual is the best and well worth it), or even free online.
Use the schematics to TS the circuit. If you don't know how to use schematics find someone who can show you. They can look intimidating but it's really just a matter of following a line and understanding a few different ways that switches and relays work.....well until it goes into a computer box...LOL

[WanderingLex]

Originally Posted by HamSkoolie

When you say you pulled "the cabin fuse panel" do you mean the panel for the BUS BODY?



I used to work on E350 SuperDuty vans with transit fiberglass 19 pax bodies.

Our buses had the standard chassis (CABin) fuse block and then a "bus board" with a circuit board, fuses, relays, and some chips. Our buses had them in the overhead at the front of the bus but that's going to be dependent upon the builder.

If ANY of these circuits were broken or the board removed, the vehicle was inoperable.

I suspect you mean that you're pulling the bus body panel and what's happening is you're interrupting a starter enable circuit.
Your rig is largely just a Ford E350 and you should be able to find the schematics via Ford, a GOOD repair manual (the Ford service manual is the best and well worth it), or even free online.
Use the schematics to TS the circuit. If you don't know how to use schematics find someone who can show you. They can look intimidating but it's really just a matter of following a line and understanding a few different ways that switches and relays work.....well until it goes into a computer box...LOL

You've got the thread of it. My body was mfg by Coach and Equipment, so the panel is over the drivers door. I suppose it's not really doing any harm being there, it just takes up valuable space (I have a little safe that will fit there quite nicely). I'm fair at reading schematics, I was looking at the fuse & relay list and it doesn't say anything about engine control. I'll have another look. But then the question becomes, how do I bypass the control module without engaging (or disengaging) it?

What if I just follow the main lines for the bus body back to where they connect to the secondary battery and disengage the whole thing there? Will the computer still freak out that it's not there, even if the circuit is complete at the battery?

Ah, the joy of doing puzzles.

[HamSkoolie]

Every upfitter (the guys that put the body on the chassis) has their own way of doing things and they also change things up based on cost savings (usually labor) or the specs given by a bus purchaser. Where I worked we ordered buses by three's and have them spaced out to help keep costs spread out. The boss spec'd them and one of the mechanics would make one or more trips to the manufacturing site to ensure they conformed to the spec.


The upfitter that built your bus may have set up the system to kill the engine if one or more (who knows what) criteria were met. For instance, rather than physically locking the shift lever with an after market part they may have used a factory interlock that prevents moving the shifter from park unless the brake is pressed.

This could still allow the bus to take off with the lift door(s) open or even with the lift deployed and that's a big OOOPS so to prevent that they might install an engine kill in the bus circuitry that if the door or lift position is open/deployed, it kills the engine if the brake pedal is touched.


That is JUST an explanation of a bus body circuit that would be designed to kill the engine. By my mind, anything that can kill a running engine is a hazardous system and I'd never design such a thing but I've seen them and they definitely lowered my opinion on the intelligence of "engineers"...... not as much as the guy who "engineered" the battery remote hot cable connection right next to the oil filter so that you could weld the oil filter wrench between that post and the oil filter.


Without being hands on or seeing the body schematic there isn't much someone can do except advise. I would suggest putting it all in so that everything works and then:


1) Opening up the lift doors, deploying the lift, opening emergency exits that are alarmed, chocking the wheels and putting the bus in neutral.....basically try to activate all the safety interlocks that may be installed.....dont' forget seat belts connected as sometimes there's an interlock circuit tied to the seat belts..... you just never know with upfitters. Does the engine start? If so you aren't likely to have a kill circuit.


2) If the engine doesn't start, begin securing each interlock one at a time until you determine which interlock kills the engine start function. This will all take a bit of time and is a pain but without schematics you want to learn as much as possible about how the system works.


3) look under the dash for any wiring additions. Particularly where wires are spliced into other wires with non factory methods. You'll mostly want to concentrate on the area under the steering wheel and down the steering column to the actual ignition switch rather than the column key lock (it's been 20 years so that may have changed). See if any added circuits affect the start circuitry with meters or selectively disconnecting a plug.


4) Do the same thing at the factory chassis fuse block and under hood/behind the dash (all depends on how they've changed things in 20 years) relays.



5) You could use a meter or test light at the body circuit panel and look for any circuits that are active only when the starter is engaged. This could lead you to a solenoid or an added circuit that disables the starter.



6) Start pulling fuses, circuit breakers, individual wires, and then any multiple wire plugs......pulling one at a time and then verifying operation until you find what is causing the issue.


The cause of the problem could be as simple a ground added to the starter circuitry that is open or closed (depending on the design) unless it receives a signal (or doesn't) from that control board for the bus body.

It could also just be an open solenoid that is only closed by power supplied through that body board.


If there is any way to get the schematics from the builder or the seller you should do so (within reasonable costs that is) and definitely get the chassis service manual and schematics as you'll be running that chassis for some time to come and this will not be the only time you'll want the manual.

[WanderingLex]

Thank you so much for your thoughtful and thorough answer!

Selective disconnecting and testing seems to get me the best results though it takes the longest - that's how I was able to get rid of the switches on the rear doors - I'll have to spend a day poking around under the steering wheel & etc.. I've already reached out to the manufacturer to see if they can be of any help. Fingers crossed!

Does it make me a masochist that I actually like beating my head on this particular wall?

[HamSkoolie]

Originally Posted by WanderingLex

Does it make me a masochist that I actually like beating my head on this particular wall?

Not at all but it will be well worth when, out on the road, some electrical gremlin appears and you understand the electrical system far more than you do now.