Stray 12v voltage - where to begin?

[Panhandler]

I was checking for voltage to the shower sump pump and found that with the 12v breaker off I was getting -2.7v. With the breaker on I was getting 13.2v. I'm assuming there should not be any voltage with the breaker off? I'll have to trace the wire, but I believe the pump is on its own circuit and comes direct from the panel. To fix it, check the breaker for voltage at the panel? If no stray voltage at the panel, pull the old wire and run new wire?

Any common causes of this? Is it unusual?

Thanks!

 

[caltexflanc]

Is the pump connected to a float switch? A ground trace would be in order as you may have another device that some PO put on the ground circuit. (Given you say it is showing "negative" voltage. Check some other devices for CB on/off voltages.

 

[Russell Clifton]

Might try this. Turn off your 12v battery switch so all of the battery voltage is turned off on the boat. Check to see if you still have the 2.7v. If it is gone, turn battery switch back on, start turning off 12v breakers, checking for the 2.7v after each one until you find the one that is supplying the 2.7v Now you should know which system is supplying the voltage. Not exactly sure what to do from this point. Good luck.

 

[Panhandler]

Thanks, good ideas!

Caltexflanc, there was not a pump switch connected when I tested the voltage.

 

[Panacea123]

Might try this. Turn off your 12v battery switch so all of the battery voltage is turned off on the boat. Check to see if you still have the 2.7v. If it is gone, turn battery switch back on, start turning off 12v breakers, checking for the 2.7v after each one until you find the one that is supplying the 2.7v Now you should know which system is supplying the voltage. Not exactly sure what to do from this point. Good luck.

Good advice!
If when the batteries are totally disconnected you still read voltage you have a stray current issue.
Put one lead of you meter on neg connector other in sump water, if you read voltage, its stray current, check bonding system and zincs