What to do after reverse polarity

[oday630]

So...after completing the exhaust overhaul, some wiring upgrades and yearly maintenance it was time to crank up the old motor! Well, the main battery wasn't fully charged, but I had a lawn mower battery with me as a back up. Unfortunately, I had a massive brain fart and attached the battery backwards and attempted to crank. Immediately, smoke started coming from below, I turned off the battery switch and did a quick assessment. I found that one of the terminals on the battery was almost fully melted. Smoke was also coming from around the starter, solenoid, and generator. I did notice some melted insulation from the big wire that connects the generator to the solenoid. After the smoke cleared, I disconnected the batteries and made sure nothing was smoldering, I went home before causing anymore harm.
When I return to the boat, what do I do first? What do I need to check and in what order, before trying to start the motor?
The motor is a Universal M-12.

 

[Jackdaw]

Ouch. You basically created a positive ground system. And while much DC equipment will run with a positive ground, just backwards (and sometimes disastrously so); the biggest issue is that much of the gear will have grounded frames which means the frames/chassis of all these things were energized, causing potential shorts, and you know; mayhem.

I don't know where to tell you how to start. Perhaps Maine will chip in soon.

 

[Captmayhem]

connect the battery correctly and isolate each and every circuit before turning the battery switch on.
Repair/replace any melted wires you see first!!
then one by one, check each circuit to find how much money the brain fart is going to cost you(ouch)

 

[GGordonWoody]

Sounds like the motor took the hit (sorry), but only because it's too big to protect (current-wise, that is). But like JackDaw mentioned, marine instruments are expensive because they often include protection (idiot diodes), or can even operate with the supply reversed (bridge rectifier). And some are just lights! So hopefully, all that stuff worked and you didn't burn out any of your new wires. But I think you can ring it out before you reconnect power. I would disconnect the starter cable, open all the breakers, and measure the resistance between the red cable and the black cable. Then throw each breaker and turn stuff on to see how it goes. Zero ohms would be bad, as would infinity or beyond. Good luck.

 

[Bill Roosa]

as JackDaw indicated you created a positive ground system so the first place to look is where you have a diode that normally would not pass current but is now connected backward. The solenoid, starter, and wires don't really care (the starter will try to run backward though). I'd check out the resistance between the alternator + terminal and the engine block (or dedicated negative terminal on the alternator if that is your setup). The bridge rectifier is probably shot. disconnect the alternator + terminal and any other regulator wires before testing. Depending on the alternator model you may be able to repair it yourself for just a few bucks (mouser.com or digikey.com are good sources)

 

[LeslieTroyer]

did you have the partially charged battery in the circuit also -- connecting a battery backwards by itself shouldn't cause melted wires or excessive current flow (it may pop some electronics - but again no major current like you were describing) -- if the other battery was there then yes you would have lots and lots of current flowing -- with singed battery cables causing most of the smoke. I've converted several old cars from Positive ground (damn English & Italians) to negative - with no major smoke or isolation of existing components

 

[oday630]

wow, I didn't think about everything else connected to the 12v circuits (pumps, radios, lights...), fingers crossed on those. I did have both batteries connected at the time. the battery selector switch was on batt 2, which was the good battery. I do have the jumper wire from alternator to the starter, and this is one of the wires that was burning. I did attempt to start the motor, which includes turning key (fuel pump), and pressing button for glow plugs and starter. I will make the trip early next week to assess the damage and start a new shopping list. How would you recommend checking the alternator/voltage regulator?

 

[Stu Jackson]

How would you recommend checking the alternator/voltage regulator?

Reread Gordon Wood's post. Do one thing at a time, ONLY one. A good friend once told me: "If you do two things at once and one doesn't work, you won't know what was at fault."

Get the reversed battery outta there, hook up your good battery, and get to work. Make a checklist first, 'cuz you know your boat better than any of us do.

After you get the "passive" 12v things sorted out (and we all hope nothing is fried), then replace the burned wiring from the starter to the alternator, and energize the system looking for any more bad stuff around the engine. Then and only then start 'er up, and measure the alternator output voltage.

Least that's what I'd do.

If you have alternator issues, consider finding a good alternator repair shop locally, or, if you're up to it, follow Bill Roosa's ideas.

Good luck.

 

[GGordonWoody]

did you have the partially charged battery in the circuit also

Ha! Good read. @oday630 posted after yours that the battery switch was set to position 2 (house?), but on some switches it looks like you might have to go through the ALL position to get from 1 to 2. So IDK. The ALL position would start some evil for sure. One big marine battery humpin' some little tractor battery might melt off the terminals of the lesser, and maybe the switch. But the little battery would be so busy it wouldn't have anything left for the motor. Nah, I'm thinking the tractor battery was never connected to the bigger battery, not for any length of time. I'll bet if @oday630 fixes the motor and melted jackets she'll be fine. Sorry @oday630, I can't help with the solenoid or alternator. I might drop them off or over the side and get new ones.

Here's a pretty good video on the guts of an alternator.

So, for the record, I did exactly this back in the Spring. My ship was new to me, I connected the red cable to (+), and solid black to (-). No motor, so no problem, everything worked fine. I only discovered the problem at the slip after repeatedly blowing the fuse in my Garmin Nuvi. Red was not hot and I never traced the cables aft. I covered the red with electrical tape and updated my diagrams. Very embarrassing.

 

[Richard19068]

Sorry I don't have any help, but on the lighter side, you might need some of this, adapted for your particular engine of course:

http://www3.telus.net/bc_triumph_registry/smoke.htm

 

[WayneH]

Sorry I don't have any help, but on the lighter side, you might need some of this, adapted for your particular engine of course:

http://www3.telus.net/bc_triumph_registry/smoke.htm

I've needed this kit for all the times I've released the magic smoke from the wires. Just ordered two kits for my Garmin Map72 cuz it needs lots of help.

 

[dreuge]

Sounds like you may not have line fuses such as MRBF installed. It maybe too late for the damage done, but consider adding them as part of the repair. Cheap insurance for those brain fart days we all have.

 

[Patrick Boylan]

If you care to skip steps at no cost other than labor, remove the alternator and take it to an electrical repair shop that will check for free. I also hooked up a battery positive and negative wrong. My new battery's label was upside down. I oriented it label rightside up, like my other battery, and never paid attention to the etched + and - signs. I got smoke, spent more than a month trying to trace wires one at a time. The most obvious symptom was that the oil sensor light and buzzer sounded when I turned on either battery, and had to endure all the 'disconnect the buzzer' advice.
I hesitated to remove the alternator because I feared it would cost money to have it professionally examined, and typical fear because I'd never removed, let alone successfully reconnected, one. Someone told me where to find a shop that does alternators, they charged nothing for the appraisal, $120 to rebuild it, and for free they replaced a stripped bolt.
Meanwhile I had disconnected and reconnected many wires, stripped threads and had to replace an oil sensor.

 

[Norden Guy]

On a lighter note........my son told me my computer runs on smoke. When the smoke comes out it will not run anymore.

 

[oday630]

I was able to get to the boat today and do a lot of looking and testing. Yes, releasing smoke does cost money! I removed and tested the starter(still working), alternator (released more smoke, so I will need a new one), battery (will need to replace both). The battery wire that connects to the starter was the one the was smoking. Luckily, the battery switch and all switched on the panel checked out with the ohm meter. But, only a new battery and power up will confirm what really works.
I have been reading and researching about the alternator for this motor M-12. Will it be possible to install and run the damaged alternator until the new one arrives? I only need the motor to leave and return to the slip. I was thinking of installing it, but not connect any wires to it, basically use it as a pulley. Will the motor still run without alternator hooked up? We have a club race coming up and I did't want to miss it. But, I also don't want to ask for help and have to tell them about my oops.

I will be putting on fuses at the batteries! But what is the appropriate size 200 amp? I plan to put on ACR for battery charging. Thanks to all for your help. Hopefully, I'll be ready to sail soon.

 

[Charles Erwin]

Your problem might be an opportunity.

200 amp fuses (one at either of your two battery sources) may permit adequate and reliable current to flow to the starter but you need to make inquiry. Too small cable - battery to starter - is one of the most common goofs I find in sailboats. So installing larger diameter cable (larger than you are using now) in the path from battery to starter is a very good improvement.

Size of cable is easy to calculate. Look at starter drain, distance to battery, then wire size. No more than 3% loss is just right.

Here is a calculator http://www.genuinedealz.com/voltage-drop-calculator.

Charles

 

[Bill Roosa]

The motor will run fine even after the batteries are dead provided you do not have an electric fuel pump in the supply line. Given that the cables did not melt but only smoked the insulation I'm thinking that the alternator diodes blew and created an open stopping a catastrophic fire. Another case of the good Lord looking out fro dummies. Welcome to the club BTW. If just the diodes blew you can replace the diode pack fairly easily.

 

[LeslieTroyer]

you can probably have that alternator rebuilt for a lot less than a new one. As long as you can start the thing you probably get by without much other battery (a lot of them will run without the fuel pump) - I'm surprised the alternator was toast - maybe the diodes -and regulator - but the alternator itself should be putting out AC.

Les