Hi all, I'm hopeful several of you can offer a solution to our bilge fan issue. We have two bilge fans for engine venting prior to starting or when needed. Both fans worked last year when boat was winterized and wrapped. They did not work when the boat was placed back in the water 3 weeks ago.

I disconnected the power and ground wires to the fans and checked voltage while switching both bilge fan switches independently on. With either switch on the wire leads to the bilge fans have 12+ volts.

I then thought, OK maybe the fans both stopped working. I connected each fan to one of the batteries in the boat and both immediately worked.

Next, I connected the fans back up and tried each switch. Fans did NOT work. Ok, scratching my head a little now.

With the fans connected I then checked the voltage again while independently turning on each fan switch. ZERO volts with the fans connected???

Why would I get a good volt reading with the fans disconnected but ZERO volts with the fans connected?
Is this a relay issue or possibly a ground issue?

I have a wiring diagram but I'm unsure what the relays look like or where I can find the common ground location for the bilge fans. (It appears that several components ground to a central location)

Also, the 12 volt panel has a switch to cut bilge fan power, but this was in the on position while performing my checks.

Any and all help is greatly appreciated!