Volt meter

What makes a volt meter peg out when you turn me on and then go back to middle when you turn key off.

Forgot to send the other photo

Take a handheld voltmeter and measure between + and ground with the key off. It should read 0. With the key on it should read the standing voltage of the start battery, 12-13 volts. If that is the case then the meter is bad. If it reads any differently, don’t do anything until you find out why?

Tom

First thought is a bad meter, this can be easily verified with an external voltmeter, measuring between the + and - on the back of the meter. If that measurement is the same as the boat's meter start checking ground integrity.

Either static electricity or magnetic field caused . It’s probably not your actual voltage going up

Thanks guys. Will let you know what I find.

Let's you know it's working. Turn on the power and the needle does a full sweep.

I have seen that before. I believe that is normal due to how the voltmeter is built.

Keep in mind, that type of meter uses a coil and magnet. Its mechanical. Its not only seeing volts but amps and along with its internal resistance. I think Arc hit it right. A magmatic field develops from the voltage drop going down and back up again for that spilt second.

Hook a simple 12 v test light between the meter terminals. If you get a bright flash when the meter pegs, it's real. A digital meter might not scale fast enough to read the spike before its gone.

It doesn’t make a sweep. It just stays there pegged when you turn key on. Will check with meter. Thanks

captbuddy said:

It doesn’t make a sweep. It just stays there pegged when you turn key on. Will check with meter. Thanks

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And when the engine starts, does the meter return to the proper reading?
If so, dont worry about it. Normal.

captbuddy said:

It doesn’t make a sweep. It just stays there pegged when you turn key on. Will check with meter. Thanks

Click to expand...

Your pic shows the meter at just over 13 volts. Thats normal of course. Are you saying you turn the key to on and the meter stays pegged? Or it is just pegged for a second? In ether case, after starting the meter goes to 13v as shown.

The meter is at 13 when key is off. As soon as you turn key on the meter is pegged and when you crank the engine it stays pegged. I thought maybe it was because I had inverter charger on when I cranked it. But it did the same when I shut inverter and charger off. Haven’t had time to put volt meter on it.

Is this a new boat? Has it recently had work involving electrical?

Occum's Razor says it is a bad meter. Thats my bet. I put overwhelmingly odds there. Depending upon how the meter works the deflection is overcoming some other force to move (fixed magnet, spring, dynamo, etc, etc, etc). If anything goes wrong with this opposing force, the meter pegs.

Of course if two 12v batteries got wired in series instead of in parallel and you've got 24v on your 12v system, the meter is properly pegged -- and the electrical system is dangerous.

As suggested by others.....check with another meter ....before...playing with sparky.

Once you start the engine, does it read normally, or does it remain pegged the whole time the key is on? Gas or Diesel engine? Any 24V parts to the system?

My guess is the needle has slipped on the shaft. But this is easy to sort out with a DVM as suggested.

lwarden said:

My guess is the needle has slipped on the shaft. But this is easy to sort out with a DVM as suggested.

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Interesting theory. So with the ignition off, the meter should be reading zero, but because the needle has slipped it just happens to be on 13V and appears to be a sane reading. As you say, a DVM would tell you right away.

Has a multimeter been used to see what the input + wire is bringing to the meter grounded in different locations? How about polarity?

Not yet.

captbuddy said:

The meter is at 13 when key is off. As soon as you turn key on the meter is pegged and when you crank the engine it stays pegged. I thought maybe it was because I had inverter charger on when I cranked it. But it did the same when I shut inverter and charger off. Haven’t had time to put volt meter on it.

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Sounds like broken gauge mechanical bits. Confirm with a DVM.

Is that KOEO or KOER. That would be the difference between an instrumentation issue vs a possible alternator output problem. With key on engine off it couldn't possibly be over voltage from the batteries alone.