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ContinuousWave: Small Boat Electrical
Erratic Voltmeter Readings
|Author||Topic: Erratic Voltmeter Readings|
posted 04-28-2006 04:17 PM ET (US)
I have a 1995 75-HP Mercury. The voltmeter spikes to 18 volts intermittently. My warning alarm also goes on when the voltage spikes and goes off as it drops to normal. This started last season. This season I put in a new battery. Went all day without a rise in voltage, then. all of a sudden. it starts fluctuating again. This was during a very long choppy ride back to port. Also, my instrument lights work intermittently. There are three of them: gas gauge , tach and volt gauge. Sometimes only two of them work; sometimes one; sometimes all three. Also, the gas gauge itself seems to jump all over the place at times. Can all this be due to a bad regulator? Does it sound like a short somewhere? Which wires would I need to check to look for a short in the system?
Also, I ran the boat only once with the brand new battery and ran it just long enough at higher volatges to get back to the dock, about 10 minutes and it fluctuated at that. Did I destroy my new battery?
posted 04-28-2006 04:33 PM ET (US)
Your battery is probably OK, but keep an eye the water level.
Bad regulator or bad connection.
posted 04-28-2006 04:47 PM ET (US)
Thanks chuck , but the battery is sealed. I just want to make sure I didn't cause any gas build up.
posted 04-30-2006 11:12 PM ET (US)
I had the same symptoms and found a broken ground wire in my control harness, where it flexes the most outside the transom.
posted 05-01-2006 01:41 AM ET (US)
I'm relating automotive rather than marine experience here, but I think the effect is the same. Voltage spikes usually come from the voltage regulator. This can kill batteries instantly. You may be able to clean the contact points in the voltage regulator. If the voltage is wrong, you may expect the guages to be wrong as well. I had a Ford with an extra regulator for the instrument panel. When that would fail, all the gauges would peg at maximum. Good luck in chasing this down. Dave
posted 05-01-2006 02:47 PM ET (US)
Brian - where would I locate the control harness??
posted 05-01-2006 03:21 PM ET (US)
Sorry for being vague.
I was referring to the main wiring harness that carries all your instrument signals and controls to and from the engine.
It runs from your ignition switch to the engine and is a multi conductor cable.
Inspect it wherever it is accessible and look for breaks or chafe marks in the outer insulation. If you find any you may have to open it up and repair individual wires inside.
It is easier than it sounds.
You could also verify by putting a jumper from your instrument panel ground to another ground point behind the dash,perhaps on your fuse panel, bypassing the wiring harness ground.If things start working normally the problem is definitely your harness ground conductor.
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