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Old 07-22-2017, 10:31 AM   #1
Mini-Skoolie
 
Join Date: Jul 2017
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Bus won't start after snipping stop sign

Greetings. New to buses, new to diesels, new to chopping into vehicular DC! After searching here and on the google I've found myself stuck on what to try next, as my 2007 GMC short bus won't start anymore (and an alarm goes off) after the latest round of modifications. Here's the bus:




Here's what I've done and tried so far:

1. Removed the hood fisheye mirrors and capped what I assume were defrosting circuits that were integrated into the mirrors. Looks like this:




2. Snipped of the side stop sign (flashing).



Red wire is hot (12 v) when the bus is on, otherwise not. The two smaller gauge pairs were badly corroded even where I cut them, mid-length.

Here's the type of sign, if it helps any:




3. Removed a bunch of seats (probably irrelevant!)

4. Let the bus sit for two days and allow the kids to open and close the door (electric) about 50 times or so.

5. Per a post on Skoolie.net, I tried capping various pairs of wires from the stop sign. Nothing seemed to change.

6. Thinking that perhaps my battery was just low, I hooked up a booster-type auxiliary battery for a few hours, which brought the voltage up from about 9.8v to 11.84 V. Some of that improvement may have come from sanding the contacts. I have a battery tender gizmo that I'll hook up when I can find the thing.

Here's a vid of what trying to start the bus looks/sounds like at the moment. Any and all advice appreciated. At this point I'm not sure what to try next.

Short Bus Won't Start after Snipping Stop Sign Electrical
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Old 07-22-2017, 11:39 AM   #2
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Location: Winlcok, WA
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You have some sort of interlock that is not allowing the starter to engage.

If an alarm is going off that is a clue that something is not closed properly.

At a guess I would start with the rear emergency door and make sure the door is all the way closed and latched and the vandal lock fully retracted.

I would then make sure the roof hatch is down, secure, and the lock is fully engaged. Roof hatches are notorious for not closing securely allowing the open alarm to continue to buzz even though it appears as if it is down, secure, and locked.

You may have a no-child-left-behind button at the back of the bus. That one can be a real bugger to reset and may require disconnecting the battery.

The mirror heat and stop sign should all have on/off switches. There should not be a hot wire going to the stop sign except for when the master switch is activated.

I would also try putting the gear selector into neutral to see if it will engage the starter when the key is turned. And then try it in Park again.

Other than that, I have no clues.
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Old 07-22-2017, 12:15 PM   #3
Mini-Skoolie
 
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Thanks for the advice, cowlitzcoach.

I went back and double-checked the back door, and it seems fine. Don't have a roof hatch. As for the switches for the stop sign, etc. I'm not too sure which ones they are!



Probably "Master"?

Flipping on and off the defrost circuit does cause the electrical situation to change, but it doesn't allow the bus to start.
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Old 07-22-2017, 02:11 PM   #4
Mini-Skoolie
 
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Here's an update: hoping to eliminate some variables I've rewired both the stop sign and the fisheye mirror defrosting lines. The bus is still behaving as though it's infested with electrical gremlins and won't start.

Interestingly, when I turn the bus on, the stop sign automatically "closes" whether the master switch is on or off, so it has constant power.

There is still a rapid alarm chime when turning on the bus. While it's possible I messed up the re-wiring I've checked it now a few times.

After the bus is off, we hear a rapid chiming from the little speaker at the back of the bus.

Stuck and open to suggestions!
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Old 07-22-2017, 05:04 PM   #5
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What is your battery voltage after all this trying?

John
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Old 07-22-2017, 05:56 PM   #6
Mini-Skoolie
 
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I found my trickle charger, so now both batteries read 12 V the whole time.

The way the electrical system flickers makes me think there's a poor contact *somewhere* but I can't figure out where it is. The persistent "rear speaker" beeping makes me think maybe it's the wiring for sensing the back door being open that perhaps got dinged during the seat removal?

Lacking ideas to try, I spent the rest of the afternoon touching up the paintjob. It can't move, but it's shiny.
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Old 07-22-2017, 06:34 PM   #7
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I almost made the same mistake with my stop sign. As I started to cut one of the wires I immediately heard a very faint buzzing sound. There were a few wires and I'm not sure which color it was....I'm thinking it was the green wire but that doesn't matter at this point. I backed off right away and decided I better trace them and disconnect from the main panel....no problems from there on out.
I've heard of too many people cutting away at their wires and then not being able to start their bus with loud buzzing alarm noises. I learned from others'mistakes.
You'll save yourself alot of time and troubleshooting if you trace them back to the main control panel and disconnect.
I really think this is your problem. Good luck!!

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Old 07-22-2017, 06:43 PM   #8
Mini-Skoolie
 
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This sounds like good advice! I hadn't heard any horror stories before starting. At the bus dealer they made it sound like no big deal to strip off the stop sign.

I'm not quite sure where my main control panel would be on my short bus. Behind the dash?

I have 3 strategies in mind:

1) Bypass the safety features by running a jumper wire from the ignition to the starter. Inspired by this thread. I can't locate (so far) my starter under the hood so this strategy isn't going so well.

2) Fool the bus into thinking it still has its stop sign, etc. Unfortunately, even with the stop sign rewired to the bus my electrical system is freaking out and the bus won't start. Still might be the simplest solution if I can figure out what's going on.

3) Extract the safety circuits properly by excising them from the main panel. Sounds good, but I'm not quite sure where to start. My stop sign's wires disappear into an interior wall that seems to be completely closed by rivets. I'd need to drill 'em out for access.
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Old 07-22-2017, 06:55 PM   #9
Bus Crazy
 
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Coachwork: Bluebird
Chassis: GMC
Engine: Cat 3116
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To be blunt, you really haven't told us much.
What year, make of bus, engine make and size etc. would be helpful.
You need a decent electronic battery charger, not just a trickle charger so maybe purchase one now. Also an ohmeter so you can test different gremlin situations.
Time to get to know your bus is now, start digging in to what makes it tick.

John
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Old 07-22-2017, 06:56 PM   #10
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When one is removing the stop arm, and working on the doors, etc., every time you disconnect a wire one needs to make sure the bus will start. My thomas would not start when i removed the stop arm, so i went in to the wiring panel and bypassed some relay so itwould work properly. Same with emergency door on side and large window in back. Wiring is simple, just trace the circuit and repair.. Your bus may even contaain a wiring diagram for reference on the elect panel door... Mine did
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