Batteries Hooked Up Backwards

[drew78634]

My son accidentally hooked up our bus batteries backwards and caused a small fire at the starter and melted through one of the smaller wires coming off the starter. I have an idea of what to start checking and replacing (the small burnt out wire) but I wanted to check with you gurus as to what I should be checking / replacing to recover from this hiccup.

Any advice is greatly appreciated!

Drew

[alpine44]

Originally Posted by drew78634

My son accidentally hooked up our bus batteries backwards and caused a small fire at the starter and melted through one of the smaller wires coming off the starter. I have an idea of what to start checking and replacing (the small burnt out wire) but I wanted to check with you gurus as to what I should be checking / replacing to recover from this hiccup.

Any advice is greatly appreciated!

Drew

#1: Spank the kid if he should have know better. Otherwise, buy him a copy of "Electricity for Dummies".

#2: Replace everything that is obviously fried. Then hook up the batteries correctly and see what works and what does not. Anything costly that did not have reverse voltage protection and may have expired will not get any worse with the correct polarity.

#3: Trying to figure out why the small wire burned up I am assuming that you have a snubber/free-wheeling diode somewhere for the reverse EMF from the starter solenoid. Your wiring diagram will show that. That diode, if there, is most likely toast and needs to be replaced.

(Explanation: When a current flows through a coil, a magnetic field is being created. Upon stopping the current flow, the decaying magnetic field will induce a reverse current in the coil and attached wiring. That's why inductive loads created impressive sparks at contacts when being disconnected. To prevent the reverse current from eroding switch contacts or frying transistor switches, a snubber/free-wheeling/flyback diode is employed to short circuit the reverse current. However, these diodes are not rated for the current of a car/bus battery hooked up the wrong way.)

[o1marc]

Replace the child.

[alpine44]

Originally Posted by o1marc

Replace the child.

There used to be the "Cars for Kids" charity where you could donate unwanted cars.

A friend of mine photo-shopped a picture with a dumpster marked "Kids for Cars" and him holding his son up, ready to dump him for a new car. I think his kids behaved a lot better after that.

[o1marc]

Originally Posted by alpine44

There used to be the "Cars for Kids" charity where you could donate unwanted cars.

A friend of mine photo-shopped a picture with a dumpster marked "Kids for Cars" and him holding his son up, ready to dump him for a new car. I think his kids behaved a lot better after that.

It's Kars For Kids, and they are still around, heavily in my area.

[alpine44]

Originally Posted by drew78634

My son accidentally hooked up our bus batteries backwards and caused a small fire at the starter and melted through one of the smaller wires coming off the starter. I have an idea of what to start checking and replacing (the small burnt out wire) but I wanted to check with you gurus as to what I should be checking / replacing to recover from this hiccup.

Any advice is greatly appreciated!

Drew

Thinking more about the burned wire, this could also be the charging wire from the alternator. This wire would be connected to one of the big stud terminals on the starter. (My first speculation was about a wire being connected to a smaller spade or screw terminal on the starter).

There are six diodes in the alternator that rectify the AC current from the three alternator windings and prevent the battery current from flowing back through the windings when the alternator is at rest. They will short circuit a reverse battery voltage and burn up the wire leading to them.

If your burnt wire goes to the alternator, hook the new wire to the alternator via a 12 Volt bulb and check that there is no current flowing with the battery connected the right way. If the lamp lights up, the diode array in the alternator needs to be replaced.

If the lamp stays dark, connect the wire directly to the alternator and run the engine while monitoring the battery voltage. If the voltage does not increase slowly, your voltage regulator is toast. Fortunately they are cheap and easy to replace. Just search on youtube.

[magnakansas]

That wire sure sounds like a "fusible link" wont be right again until replaced. Trouble is, what size was it? Have enough left to identify? Go through the fuse box and check them... When ever I have seen battery installed backwards, usually main fuse, on a honda, 80 amp, was blown, some times one or two more, but usually just the main fuse.

william

[drew78634]

Thank you all for your helpful advise. I'm jumping on this issue today after work.

Drew

[drew78634]

Update: Received a set of wiring diagrams from one of the bus gurus from here and got under the bus today to remove the burned our wire. It appears the wire which burned out was a 10ga fusible link. I started to trace back the wiring harness the link was inside but it's a bear to get to. I will have to remove the air filter to get better access to the harness. As I was starting to pull down the filter assembly a wasps nest fell down in my lap!!! Luckily I was able to move at light speed, not bad for a 45 year old guy, and didn't get stung. I will be taking a couple cans of wasp killer tomorrow to eradicate any other unwelcome bugs I might have in the engine compartment or in the under carriage.

Again, thanks for the advise and insight. With any luck I can get Abigail back up and running soon.

Drew

[drew78634]

He's a good kid, just made a silly mistake. All in all, if that's the worse decision he makes at his age (17) I think I'm getting off easy. He would rather be out working on the bus than running around with other teenagers getting into who knows what worse kind of trouble!!!

[Danjo]

Originally Posted by drew78634

He's a good kid, just made a silly mistake. All in all, if that's the worse decision he makes at his age (17) I think I'm getting off easy. He would rather be out working on the bus than running around with other teenagers getting into who knows what worse kind of trouble!!!

Yeah, at 17 I had a short in my pickup truck and not listening to my dad I continued to mess with it and ended up making the tail end wiring harness light up like a Christmas tree.

Note to self - Mark the positive terminals with a 4” wrap of red electrical tape!

[CHEESE_WAGON]

Originally Posted by drew78634

He's a good kid, just made a silly mistake. All in all, if that's the worse decision he makes at his age (17) I think I'm getting off easy. He would rather be out working on the bus than running around with other teenagers getting into who knows what worse kind of trouble!!!

Could've been worse. At least nothing caught fire, which is a possibility in some situations. At least he's keen on helping, and presumably likes the idea of a skoolie. Most kids today at that age would be "You want ME to get on THAT thing? EWWWWW..."

As we rapidly approach 2029, methinks if history repeats itself, these same people who turn up their nose at bus conversions will practically beg for one in a depression the likes of what the US had from '29-'39 or so.

[drew78634]

Originally Posted by CHEESE_WAGON

Could've been worse. At least nothing caught fire, which is a possibility in some situations. At least he's keen on helping, and presumably likes the idea of a skoolie. Most kids today at that age would be "You want ME to get on THAT thing? EWWWWW..."

As we rapidly approach 2029, methinks if history repeats itself, these same people who turn up their nose at bus conversions will practically beg for one in a depression the likes of what the US had from '29-'39 or so.

You're not lying. My father in law, a very wealthy Doctor, now wants me to build him a skoolie instead of wasting money on a Class A motor home. The movement is getting more and more traction as the economy spins out of control! I will be happy to move into my bus and get away from $6000 / yr of property tax on a $240K house!

[drew78634]

I finished tracing out the burned out wire as a result of the battery mix up. It was a 10ga fusible link. It looks like that is the only casualty of the power surge. I however don't know where the fuses are. Anyone have an idea where I can find the fuses on a 1992 Blue Bird All American RE.

Thanks Y'all,

Drew

[Danjo]

Would it start?

[Native]

It does not sound like he has had time to replace the fusable link and try to start it.

[drew78634]

No, I had to disassemble the air filter assembly. I'm going to clean up the filter, and the visible corroded connections to the batteries before I reinstall everything before I attempt to restart the bus.

I'm considering rebuilding the hydro system since it's visibly leaking a lot of oil. Might as well since I have the time and it's already in a state of disassembly.

Drew

[drew78634]

Got the fusible link reinstalled, and all the electrical lines rerun in their proper place. Engine started right up like a champ.

Next step is to replace all the fluids and filters...she's been sitting a while.

Thank you for all your help during this troubleshooting adventure!

Drew

[2kool4skool]

[Native]

I am so glad you got it running again. Whew!