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Old 06-03-2021, 07:15 PM   #1
Join Date: May 2021
Posts: 10
Unfortunately I have joined the gang. I messed up.

I hate that I'm adding to this. Should've done the research but long and behold I am now a member of Team "won't start". Had a mechanic come that I can confirm had no idea what he was doing- said I needed to reset my ECU and unplugged some other stuff. Mainly around the batteries. I can no longer reach him.

The bus: 2008 GMC Savana 3500 6.6 Duramax Cutaway Thomas build.

We gutted it. Saw the 1000s wires- decided without reading they must've just been for the heat, A/C, lights, and speakers...Ripped them all out.

The main panel or fuses and relays for every wire was located above the drivers seat.

They came from a black tube coming from the ground right behind the drivers seat.

Here are a few pictures of what was, and what now is and a list of what every wire says on it.
The pic next to the amazon envelope is where the black tube is right behind the drivers seat. The pic of all the wires is.....all the wires.
The pic of the panel is before I cut everything. I also took note of what most of what was hooked up to each relay.
I thought worst case scenario- the wires hooked up to the fuse need power...Take everything that isn't a ground- apply power. Ground the grounds..should be good? I haven't tried that- but those are my thoughts.

Please someone point me in the right direction.
1 yellow spare e

1 tan child Ck

1 tan dome lt

2 thick red vandalock

1 red pilot

1 green flash sw 23c

3 no label yellow

1 brwn marker lt

1 grey master 3a

1 yellow amber sw

1 green eight turn

1 green spare o

1 blue step light

1 blue a/c

1 blue cross gate

1 orange ac comp

3 red ignition

1 red htr hi

1 green htr low

1 purple ignition relay

1 red stop arm pwr

1 orange pilot

In addition, my batteries on the side of the bus died. I took them out to charge. When I replace them I parralleled them, hooked up the ground to the ground and the red positive to the positive. Upon further investigation- there appears to be 2 red wires that need to be hooked up. 1 already had a source of power going to it. Not sure where from since the bus was not running. There is a battery under the hood- but why would it be providing power to the other 2? picture of battery tray with the 3 connecting wires

In addition x2. After investigating the battery under the hood I noticed the grounding wire had this little attachment on it as if something else should be grounded, I could not find a loose male wire anywhere.- picture with yellow piece coming from battery connecting wire
Attached Images
File Type: jpg photo-1(4).jpg (244.6 KB, 25 views)
File Type: jpg photo-1(2).jpg (142.8 KB, 15 views)
File Type: jpg IMG_1463.jpg (291.1 KB, 15 views)
File Type: jpg IMG_1464.jpg (190.9 KB, 16 views)

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Old 06-03-2021, 11:09 PM   #2
Bus Nut
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Join Date: Dec 2016
Location: MONTANA
Posts: 416
Year: 1995
Coachwork: AMTRAM
Chassis: INT
Engine: DT466
Rated Cap: Big Girl
Dude not to be negative but If you really just started cutting wires and ripping them out.... what were you thinking??

Your only hope now is finding a service manual for the chassis and bus body. Does it even crank? A 2008 is pretty new they gobs and gobs of wires. If you can’t do the diagrams and work yourself take it to a bus dealer and be ready to write a check for more then you paid for it likely.
My Build Thread:
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Old 06-03-2021, 11:48 PM   #3
Bus Crazy
Join Date: Oct 2020
Location: Near Flagstaff AZ
Posts: 1,003
I can't help with all the little wires...but let's start with the battery cables. Your bus is a 12V system so all the batteries in the bus will be wired in if any one is connected to a battery all the other cables are therefore connected to the battery...which means all the other battery cable positives will be hot, even if the engine's not running. That makes it important to protect those other cable ends when you are connecting batteries. If you connect a battery and another, loose, positive cable touches the frame or a ground then you'll get sparks...and maybe a fire.

As far as that pigtail with the yellow butt connector the open end actually open or does it look like it was crimped onto a wire which pulled free? It looks uncrimped, which means it may very well be a spare ground point for an accessory.
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Old 06-04-2021, 09:02 AM   #4
Bus Crazy
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Join Date: Aug 2019
Location: Moved to Zealand!
Posts: 1,517
Year: 2002
Coachwork: Thomas
Chassis: Freightliner FS-65
Engine: 7.2L Cat 3126 turbo diesel
Rated Cap: 71 passenger 30,000 gvwr

Um, try posting in the mechanical forum here --

Maybe someone with the SAME bus can share with you what the minimum necessary wiring is to have a functioning bus...

An automotive electrical specialist will cost more per hour BUT they'll actually know exactly what they're doing and take way less time rewiring your bus...

Beg a fellow traveling skoolie here with the same bus to come visit you for free room and board while you look at how their bus is wired and put all your wiring back...

I hope you've learned a valuable lesson going forward...

The Murder Bus
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Old 06-04-2021, 10:19 AM   #5
Bus Nut
Join Date: Feb 2019
Location: Communist State of New Jersey
Posts: 392
Year: 2004
Coachwork: IC
Engine: T444e
Rated Cap: 27,500
I did a Google search for 2008 GMC Savana wiring diagram and got a number of hits. No way I can know which diagram is the one you need.

You may be able to find the interior wiring diagram by searching for the Thomas identification numbers and/or the VIN #. I have an IC200 and I found a lot of the manuals I need using Google.

Pictures and videos of the "before" are your friends.
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Old 06-04-2021, 11:57 AM   #6
Bus Crazy
Join Date: Sep 2018
Posts: 2,328
Year: 2007
Coachwork: Thomas Built
Chassis: Minotour
Engine: Chevy Express 3500 6.6l
Hereís the wiring diagram for the 07. Itís likely the same.

Itís a good idea to get on the AC Delco site and pay for a 2 day subscription. Youíll find a crank-no-start troubleshooting checklist that can hopefully help you figure it out. Youíll at least be able to narrow it down
Attached Files
File Type: pdf Minotour_elect_board1.pdf (293.0 KB, 12 views)
File Type: pdf Minotour_elect_board2.pdf (231.2 KB, 5 views)
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Old 06-04-2021, 12:08 PM   #7
Bus Crazy
Join Date: Sep 2018
Posts: 2,328
Year: 2007
Coachwork: Thomas Built
Chassis: Minotour
Engine: Chevy Express 3500 6.6l
I have the same or similar bus. The “Express” model. I don’t know what the difference is. Same motor. Same bus body.

PM me your number I may be able to help you a little
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Old 06-04-2021, 04:26 PM   #8
Join Date: May 2021
Posts: 10
thank you. The batteries are in parallel. I used a multimeter after taping everything.

I am now getting power to the dash. So I believ I just had dead batteries.
I assume my next step is learning which fuses have power.
If I am getting power to the ign.

If I am getting power to the ECM
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Old 06-04-2021, 11:26 PM   #9
Bus Nut
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Join Date: Jun 2020
Location: Long Beach, CA
Posts: 471
Year: 1998
Coachwork: Blue Bird
Chassis: TC1000, 40' MPV
Engine: 5.9 Cummins/B300 trans
Rated Cap: U/K
Find out what feeds the 2 fuse blocks on the left in your first picture. It should be a solenoid or relay (or two). Energize that with the key on and see what happens.
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Old 06-12-2021, 08:55 PM   #10
Join Date: Jun 2019
Location: GA
Posts: 17
Year: 2006
Coachwork: Setra
Chassis: S 417
Engine: 12.7 L
Rated Cap: 56
possible option. Go to a salvage yard or pick a part. find a bus. cut black connecting group of wires before they spread out. buy everything downstream of that junction and disconnect everything on the other end don't let anything move out of place (imperative) transport the entire loom and splice the matching wires upstream and replace at the connectors at the downstream end. Long shot but If you wanted to do it yourself might work
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Old 06-12-2021, 09:09 PM   #11
Bus Nut
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Join Date: Jul 2020
Location: Sacramento
Posts: 994
Year: 1999
I ripped out all my 'bus' wires and the engine still ran, e450. I had the chassis wiring manual though, and have wired a few cars from scratch, so had no worries.

You need a manual (does need to be a bus, but the van) to focus on wires needed for the engine..and trans..and fuel system.
Really can't help specifically, as it requires detailed study nobody else can do for you.
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Old 07-01-2021, 05:07 AM   #12
Join Date: May 2021
Posts: 10
Replying in hopes this assist anyone else. Lord knows I’ve been through hell.
After cutting every wire I went shop to shop, mechanic to mechanic. No one wanted to take on my bus- I’m talking 40-50 phone calls. 15-20 shop in person visits. Not one mechanic willing.

Anyway let’s get to it. I read probably 4-5 books worth of material just to figure this out.
My bus is 08 GMC Sierra 3500 Duramax 6.6 trans tech build.
I cut out every wire above the driver seat because I saw videos of everyone else making it storage and I wanted to do so as well. Those wires were essentially chassis wires.
If you have this bus and this problem- there are two thicker red vandalock wires in the panel board. After tracing them you will find under the hood where they are attached to another purple wire. The purple wire runs directly from the ignition to the solenoid.
The series of relay connections allow vandalock to send power to your starter when you turn the key if all precautions are met. I bypassed this by wiring a push switch to the purple wire. Message me if this was horrible explaining. At this point I can pretty much name every wire and what it does in my bus.
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Old 07-01-2021, 11:49 AM   #13
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Join Date: Sep 2019
Location: Bly Oregon
Posts: 227
Year: 1986
Coachwork: Crown
Chassis: Supercoach
Engine: Cummins 350 big cam
Rated Cap: 86 passengers?
You have done well to learn your wiring so you can fix it. In my first Crown I didn't remove original wires. I don't have a schematic for a later Crown, and the wiring was probably different from one bus to the next (ie: a Washington state bus vs. a California bus has different lighting) When I brought the new Crown home the window buzzer stayed on and I found the buzzer in the electrical panel and disconnected it and could put it back if I needed to. Neither of my Crowns are disabled from open doors or hatches. On the "old Crown" my only connection to the bus wiring from RV wiring was at the alternator. Temporarily I have the generator connected to the bus alternator so that I can start the generator. This also keeps the bus batteries charged up well as the generator has a small alternator built on it. For anyone who is planning to remove school bus interlocks I would suggest knowing what it is you are disconnecting first and make only one change at a time. If you disconnect ONE wire and the bus doesn't start/work, putting back ONE wire is easy. I also suggest to not cut wires but remove from connectors or terminal strips using proper tools. If I was considering removal of wiring I would read voltage or check for continuity to ground before disconnection so that when troubleshooting you can duplicate the conditions before the change.

In the new Crown I have a second alternator mounted to the engine next to the original one, and it will be used to provide electrical power to the RV circuits when the engine is running (as well as solar power when in daylight.
The way I look at it, the bus's electrical system was designed and sized to operate a school bus, not an RV. Leaving the original electrical system intact is probably the best. When removing lighting such as flashing school bus lights I would disconnect them at the light, and cap the wiring ends.
Again make only ONE change at a time.
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Old 07-01-2021, 02:28 PM   #14
Bus Nut
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Join Date: Jul 2020
Location: Sacramento
Posts: 994
Year: 1999
Originally Posted by imxdemetri View Post
At this point I can pretty much name every wire and what it does in my bus.
For the most part, that is what it takes, and now you know how to fix it if because as you have learned nobody wants to tackle hard jobs, business wants easy work at high pay.
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Old 07-01-2021, 02:34 PM   #15
Bus Crazy
Join Date: Sep 2018
Posts: 2,328
Year: 2007
Coachwork: Thomas Built
Chassis: Minotour
Engine: Chevy Express 3500 6.6l
Congratulations on working through it. Now you know you can fix anything
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Old 07-01-2021, 03:15 PM   #16
Bus Geek
Join Date: May 2009
Location: Columbus Ohio
Posts: 15,410
Year: 1991
Coachwork: Carpenter
Chassis: International 3800
Engine: DTA360 / MT643
Rated Cap: 7 Row Handicap
wow.. the purple wire!! GMC may just have never changed.. Glad tyou got it going!!!

the purple wire.. thats the starter enable wire going way way back to the old saginaw column days of the 70s and 80s...

I once bought a police impala for $150 that the owner said had a bad engine.. that it must be locked up because it would never turn over.. despite a new battery, new alternator, new starter, new distributor cap, new wires, plugs , new key switch.. and even a new carb.. (im not sure why or how they thought the carb would make it spin but they did).. the car was in my same apaerment building so when I paid the $$ and got the title.. the previous owner gladly helped me push it across the parking lot to in front of my apartment instead of his.. "good riddance" he said..

that evening of course I tried to turn the key and nothing.. dash lights came on and then nothing when I went to start position.. I crawled up under the dash and found a purple wire hanging there... seems odd i thought.. so I reached up to pull down on the harness and aloha I pulled out another purple wire that went nowhere.. so I twisted the 2 purples together and bam!! it spun the starter and sputted, popped and cracked.. which when I got under the hood the old owner apparently didnt have the number 18436572 in his head.. fixed the wires.. started up and even the A/C was cold.. hail to the purple wire !!!
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Old 07-01-2021, 06:51 PM   #17
Join Date: Mar 2021
Location: Central Kentucky
Posts: 116
Coachwork: Busless for now
Purple is my favorite color. I wear a purple t-shirt to work 3 days a week, sometimes 4
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