Thomas Minotour lights & wiring questions

[Roadside Rhythms]

Trying to track down lack of brake & taillights on 07 Chevy Express Thomas 5-window Duramax.
My guy's spent some time tracking it and says there's a short to ground after the TAIL LIGHT RELAY in one of the overhead fuseboxes, on the side that should send power to the rear lights. We also found that a 15-amp fuse in the underseat fuse box was connected to the Tail Light Relay.
(Thanks to Jolly Roger for suggesting going through fuses 7 to 22 on that board)
Right now, installing another wire to power running lights for a short term fix.
Not seeing any power at the brake pedal switch.
If we could figure where the taillight relay is pushing the power, that would help. Although it looks as if the wire loom from the back keeps on going past that overhead circuit board and the wires all meet behind the overhead control panel.
Ideas? Suggestions?

 

[AlphaHare]

On the Thomas boards, there should be a part number. The two are different obviously. I've had very good luck searching for and finding Thomas schematics with that number. Google "TBB" and the part number for instance. I have them from my Ford, but is sounds like the Chevy may be different.

On the 2008 Ford, the boards are "Board 1" 52004778 (schematic 52004770) and "Board 2" 52005370. The brake and tail lights actually come from the wiring harness associated with the trailer package and are not driven by the relays and fuses on the Thomas circuit boards. The only wires on the Ford that are distributed and controlled by the Thomas circuit board are running and clearance - too many of those to be easily done. The rest go through the board, but then are just passed through to a different connector with no further relay control. Guessing yours may be similar.

 

[AlphaHare]

2009 Minotour service manual - chassis agnostic for the most part as I remember. Mine is a 2008 and it was close enough in most aspects

 

[AlphaHare]

Last - google this: TBB 85410318 2001-02 Minotour Electrical Wiring Manual.pdf

It's too big to attach.

It's 2001, 2002, and there were differences to my 2008 (especially in harness construction), but it got me a long, long, way to understanding. Has both GM and Ford primary harnesses and diagrams near the front. The rest is pretty deep - I found most of the wire numbers were the same but may or may not have a alpha prefix on the wire itself.

Start with page 2.5 and 2.6 - you'll see the wiring breakouts for all the rear lights. Mine was almost exactly this except I don't have the connectors on the right side of the page - it's all one harness in my 2008.

Good luck!

 

[Roadside Rhythms]

Thanks so much, AlphaHare.
I got the following message from Thomas support this morning, along with a few schematics that don't want to attach for me right now:
"We have attached the Board 1 Schematic and Circuit CTP Report to help with Troubleshooting this issue.
There is a Chassis interface under the unit along the Rear Left Side Chassis Rail that we plug into to get the Brake, Tail, Turns & Reverse Signal from the Chassis to Board 1 Plug 5.
If you don't have those signals at that Chassis interface then it is a Chassis Issue"

 

[RealJPedersen]

Reached out to Roadside Rhythms with a direct message - but thought I would post to thread as well.

*** NEED HELP ***
2005 Chevy Express 3500 Thomas Minotour with 6.0 gas motor

Brake Lights Intermittent

New skoolie owner, just took fam on 3000+ mile road trip from SC to CA.. I just got pulled over this afternoon for no brake lights. (I was doing light checks at fill ups along with other check ups like oil, coolant, etc.) Not sure when they stopped working. On the side of the road, my son was pushing pedal while I observed with officer. Not working. Then all of a suddent hey started to work again. He gave us a warning and told us to get into town and get them fixed.

Obviously a Sunday night on Memorial Day weekend is... well ... tough.

For the rest of drive, the lights would cycle between working and not working. (My kids in back of bis were telling me as well as the light on the board overhead.

Using a "dummy light" :

1.) I checked the brake switch wire at the pedal. It is working / reading correctly
2.) I checked the 5 pin at the rear of the bus on the rail (left side) and it has power to the white wire (Brakes)
3.) I don't know what is causing them to stop working. - I am suspicious of the relay overhead, and wondering about it.

I don't know how to troubleshoot. It is hard to test the brake pedal switch when driving and the light stops working.

Any advice? How can I get back home (3000 miles)... obviously I need brake lights. The fact that they are intermittent is making it hard. What should I check? Thanks for amy help you guys can give.

 

[AlphaHare]

Find, check, and re-ground the lights. On older vehicles it's often the ground that goes out first.

 

[nikitis]

If both lights are failing it's not likely ground IMO. Both would be grounded on the frame by itself. It's not likely both grounds are failing at the same time intermittently.

If both lights are failing together, the issue likely has to be where they split off. the wire at some point is split to go to left and right side, so you'd have to identify where that location is. Sometimes it takes one wire to the very back above the rear door, and is spliced there. Sometimes it's in the middle of the cab, and sometimes it's split at the terminal under the left side panel. All depends on the bus and year, and there's no data I know of that suggests where they do that at but it does split somewhere.

If your skoolie is built out already the easiest place to check will be the left panel on the drivers side, or outside if your bus electrical panel is on the outside.

 

[RealJPedersen]

Find, check, and re-ground the lights. On older vehicles it's often the ground that goes out first.

Thank you for this advice. I checked the ground and it appears clean and tight.

If both lights are failing it's not likely ground IMO. Both would be grounded on the frame by itself. It's not likely both grounds are failing at the same time intermittently.

If both lights are failing together, the issue likely has to be where they split off. the wire at some point is split to go to left and right side, so you'd have to identify where that location is. Sometimes it takes one wire to the very back above the rear door, and is spliced there. Sometimes it's in the middle of the cab, and sometimes it's split at the terminal under the left side panel. All depends on the bus and year, and there's no data I know of that suggests where they do that at but it does split somewhere.

If your skoolie is built out already the easiest place to check will be the left panel on the drivers side, or outside if your bus electrical panel is on the outside.

This seems like a very likely culpret. I am on the hunt now to try and find out where that split is. I will start with the panel over the driver side. I have found in the rear of the bus a single wire that carries power to the brake lights. It is part of a very large plug that Thomas Techs referenced to another forum user inregards to his MinoTour bus. But, it sounds like the final run to the rear and the split will be up high, in that wiring loom that goes all teh way to the back under that plastic channel cover. I am going to start with the Left-Side Panel, then look over the back door, then remove that cover and look for a mid bus option. Thank you for this advice and help. (Not how I was hoping to spend my memorial day on vacation ... ha! But need to get bus on road again for the family!)

 

[nikitis]

Yeah I hear ya.

The wiring can only be a couple of ways. Either split at the panel with two runs to each light, Split in the middle somewhere, or carries a single wire up to the left light, then split off to the right light.

To me the latter seems unlikely but could be if it is becoming disconnected at the left light itself and not any further cause both are coming off.

So if only one power wire from the panel by the driver seat, then it has to be the middle or last option one.

Come to think about it, I have a 30ft bus, but I think mine splits up top above the Back windows. If you have a short bus it may be different.

P.S. I ended up washing clothes and going to Lowes and spent $200 on wood to build a huge heavy duty wall shelf for my garage. Not how I planned on spending my memorial day either.

 

[RealJPedersen]

UPDATE:
I checked the connections for the brake control switch - removed them and verified the multi-pins were tight and wires whole. Then re-inserted. The problem has always been intermittent, but they have worked all day today. I went into the closest town and bought a replacement brake light switch just in case, but the lights have been working great all day today. (100 miles of driving, many opportunities to brake) I am now guessing the problem was at the switch itself. If it happens again, I will replace the switch with the new one and then continnue to troubleshoot / monitor. I think I am good to drive from Jenner to Yosemite tomorrow.

Thank you for the help, and any input is still appreciated as I want to sort this wiring out well and need the knowledge base of this group. I have 3000 more miles on this trip to get home... but I think I am back on the road for now. THANK YOU for those who were able to chime in. - Josh

 

[nikitis]

Interesting. I'll bank this one for troubleshooting for others to check there. I suppose it could be that switch since both lights were out intermittently. You should stop by my place in Rock Hill on your way back from out West. Only an hour and 30 past your home.

 

[Jolly Roger bus 223]

get dialectic grease to go with the connection.
dont over do it but a little bit will go along way and help the connections frome corroding.

 

[RealJPedersen]

Interesting. I'll bank this one for troubleshooting for others to check there. I suppose it could be that switch since both lights were out intermittently. You should stop by my place in Rock Hill on your way back from out West. Only an hour and 30 past your home.

It caught me off guard as well. I have friends in Rock Hill... I will keep that invite in mind! Thank you.

get dialectic grease to go with the connection.
dont over do it but a little bit will go along way and help the connections frome corroding.

Good call re: the dialectric grease. I am going to pick some up once I am back in "civilization". We are wrapping up some time in Yosemite NP and then heading to the coast. So far, the lights have continued to function correctly. Thanks again fori all the help.