Internal Battery Short?

[LuCroix]

67 OMC Sportsman 120 if it's relevant somehow.

Last week I went to tighten a positive nut under the helm and accidently hit the ground. The wire I was tightening is the main power wire to the helm from the distribution block on top of the engine. For what it's worth I thought the battery was disconnected when I was tightening the nut. So, when I touched the ground I got a nice spark and immediately pulled the wrench off. After that I noticed that all of the positive wires had continuity to ground. I was trying to narrow down the source of the short and decided to pull both wires off the battery, no more short. I do, however, have continuity between the positive and negative battery terminals with no wires connected. Is it possible I somehow shorted the battery itself?

There is supposed to be a 50 amp fuse connected to the main positive wire of the boat but I'm assuming the previous owner removed it since there isn't one.

This is based on my assumption of no continuity without the cables connected to form a circuit.

What I did notice is that with the positive cable connected to the battery and no ground connected I have a short in the positive wires I tested.

 

[Redfred1]

To me; if you checked continuity with a meter and didn't smoke he meter; my guess is a shorted battery.Probably dead too!

 

[alldodge]

Being a 1967 I'm guessing you have points. Now if your checking from + to - cables and getting continuity I'm not to worried yet. When you connect the battery, do the cables heat up, or wires?

 

[LuCroix]

Being a 1967 I'm guessing you have points. Now if your checking from + to - cables and getting continuity I'm not to worried yet. When you connect the battery, do the cables heat up, or wires?

Cables don't feel warm at all. Wires don't feel warm at all.

I'm just assuming a short since when I turn the key to on the "on" light isn't coming on anymore and she's not cranking. Tried a few switches at the helm and nothing. Battery is testing 12 volts.

 

[alldodge]

With nothing getting hot, connect the bat and take a meter and start tracing voltage

 

[LuCroix]

With nothing getting hot, connect the bat and take a meter and start tracing voltage

Does it make sense that when I tested the hour meter for voltage both wires show 12 volts with red lead on the wire and black on the ground and neither one showing it was reverse polarity? Shouldn't one be a hot and one be a ground? Perhaps I'm thinking way too much now and just confusing myself at this point.

I also thought that voltage shouldn't be running to it unless the ignition was turned to the on position.

Could you elaborate on tracing voltage? What exactly am I looking for at this point?

 

[alldodge]

Red is 12V hot, and Black is Negative or zero. Placing a meter probe on the Red and the other on the Black the you should always get a reading of 12V. Doesn't matter if the key is ON or OFF

If it was reverse polarity the you would see -12V (negative 12 volts) if the red probe was on the Black and the black probe was on the Red

Now the Purple wire can only show 12V when the key switch is turned ON. Your way over thinking this

 

[LuCroix]

Red is 12V hot, and Black is Negative or zero. Placing a meter probe on the Red and the other on the Black the you should always get a reading of 12V. Doesn't matter if the key is ON or OFF

If it was reverse polarity the you would see -12V (negative 12 volts) if the red probe was on the Black and the black probe was on the Red

Now the Purple wire can only show 12V when the key switch is turned ON. Your way over thinking this

What's confusing me is that the hour meter has voltage with the ignition in the off position. The whole purpose of the meter is to count run time. Right now the meter is running anytime the battery is connected not just when the ignition is in the on position.

Based on the instructions to hookup the hour meter one wire is run to ground and one wire is run to a hot when ignition is on. I've got a black wire and a grey wire on my hour meter. When I go from either of those wires to ground with the ignition off I'm getting 12v. Shouldn't I be getting 0 volts when testing ground to ground? Also, being that it's hooked to a hot while ignition on shouldn't I be getting 0 volts with the ignition off?

 

[alldodge]

Also, being that it's hooked to a hot while ignition on shouldn't I be getting 0 volts with the ignition off?

Yes, so there is something that is making contact, but its not the battery. Shorting battery power to ground behind the helm could melt the wiring, blow a fuse (if there was one), burn a switch contacts. What were you adding or changing to put you behind the helm. My thought is what ever was being changed may be the reason for your issues.

 

[LuCroix]

Yes, so there is something that is making contact, but its not the battery. Shorting battery power to ground behind the helm could melt the wiring, blow a fuse (if there was one), burn a switch contacts. What were you adding or changing to put you behind the helm. My thought is what ever was being changed may be the reason for your issues.

I was troubleshooting the tilt motor at first. Ended up being that the spade connector wasn't making good contact with the fuse block. I cut off the connector and taped the wire. Next I was checking for corroded or loose wires since I was under there. Turned out that the thick green wire coming from the engine bay through the harness was loose. I went to tighten the bolt thinking I hadnt reconnected the battery yet and ended up touching it to the metal plate that's bolted behind the gauge. I got a nice spark and immediately removed the wrench. Problems seem to have started right after.

While writing this and thinking out loud I totally forgot, and was just reminded that, my nephew washed down the floor of the engine bay and the bilge area to clear out some gunk that was in there. Perhaps that's related somehow.

As you can tell I'm starting to drive myself crazy over thinking this. Simple electrical principles are turning into rocket science in my scrambled brain.

 

[alldodge]

Try disconnecting the alternator

 

[tblshur]

Might check your automatic bilge pump hope this helps

 

[SingleShot]

Something to look into is if your hour meter is in series with some other load. That is can you verify the ground lead (I assume the black) is actually at the negative of the battery? It sounds to me since you are getting 12v on both the grey and black that the it is wired between a load some where.

 

[LuCroix]

Something to look into is if your hour meter is in series with some other load. That is can you verify the ground lead (I assume the black) is actually at the negative of the battery? It sounds to me since you are getting 12v on both the grey and black that the it is wired between a load some where.

So I've been messing around with it for a couple of days and what I've noticed is that I only have an issue with everything being connected to hot and ground at the same time if the battery is connected. Once the battery is disconnected everything seems normal. Hot only has continuity to hot and ground only has coninuity to ground. Should I just hook up a new battery and see if the problem persists?

The battery it around 6 years old and I'm wondering if I did something to it when I accidently touched the hot to ground.

 

[tblshur]

LuCroix sounds like your key switch may be bad . hour meter should not be on if key switch is off.

 

[alldodge]

The battery it around 6 years old and I'm wondering if I did something to it when I accidently touched the hot to ground.

Most lead acid batteries will not last that long. If it was an AGM then a better possibility.

 

[StarTed]

I think SingleShot might be on the right track. You may have a bad ground between some other instruments and the battery. That way you could measure +12 volts on both sides of the tach. It could be getting the 12 volts through another instrument. Try connecting a 12 volt light bulb circuit tracer to both sides of the tach with the meter connected to the light probe. The load should pull down the ground side some.

Hope that helps.

 

[LuCroix]

LuCroix sounds like your key switch may be bad . hour meter should not be on if key switch is off.

Everything at the helm and the engine bay is showing hot on both positive and negative terminals. It's not just the hour meter. What I was saying in my last post is that I only have the problem when I connect the battery terminals. When they're disconnected all grounds are showing continuity to ground and not hot.

 

[StarTed]

I think you have a bad ground near the engine or battery. Check the connections and the wires to the lugs. Add a load and it should show up as a reduced voltage on the grounds

Digital multi-meters have a very high impedance so they don't add enough load to bring the voltage down on the grounds that are open down stream. That's why I suggested clipping the meter to a light or other significant load.