Overvoltage Warning - Nissan 40C

Nissan M40C - 1985 - 2cyl 2 stroke

While running slightly under wot, for about a mile, I had "overvoltage" warnings pop-up on my sonar unit. They pop-up and quickly go away. This is the first time I have noticed that. Unfortunatly, I did not switch the depthfinder into dianostics, which would report the actual voltage. Looking at the schematic, it appears to be just a full-wave bridge, fed by magnetic coil. I will ohm out the bridge, to see if there is a blown diode.

I suspect, given the type of charging system, that this may be normal. It might have been the fact that the battery was fully charged the day before. Is there anything that can be easily added to prevent the over voltage? or do you just turn on some more accesories, such as lights?

Re: Overvoltage Warning - Nissan 40C

Not really. That model was unregulated so you could get 13.5 v hitting your equipment. But, usually the battery acts as a buffer. Try putting any other leads like lights, etc, between the engine terminal leads and whaver lead set you have that feeds the sounder. .

Re: Overvoltage Warning - Nissan 40C

Elvin,

Power is run to a fused/bus/switch set-up. Power is distributed from there for lights, accesories (depthfinder), and bilge pump. At the battery, I just have the engine wire terminals, feed to power panel, and onboard charger. Trolling motor battery is on its own system and the other outlet of the onboard charger was not hooked up to it. (ie completely isolated) I should be going back out this coming Sunday and will monitor the voltage at wot.

Re: Overvoltage Warning - Nissan 40C

Had the boat out last week and received the over-voltage warning during a 2 mile near wot run. Put depth finder in diag mode, to read voltage. Voltage reading was 16V. After getting home, noticed battery low on water, so filled and recharged. I haven't tried to find diode bridge and meter out, yet.