I've got 14+ volts going to the ignition key switch. When I turn the key on, I only get mid 12s out of the switch, while still having 14+ volts coming into the switch. So, I replaced the ignition key switch thinking it must have a bad connection inside it. New switch, same results. The switch was a name brand unit, brass case looked quality like the original unit. The voltage gauge on the dash shows mid 12s which matches my meter readings coming out of the switch.

I've got another voltage gauge down in the cabin, and it shows 14+ volts coming direct from the battery.

Weird. Any ideas? Boat runs fine by the way and everything works.

Normal to see a little drop across the switch, not sure that 1.5v is really normal though. I'd check all the connections / crimps to be sure there's no corrosion anywhere... But that said, if everything works, I probably wouldn't stress about it.

Mid 12’s is what you’ll see when engine not running. As you did when you turned key to on.

Maybe I’m misreading ?

How are you getting 14V with the engine off? An AGM battery should read around 12.7-12.8V fully charged

Mirage,

Voltage is pressure. Think of it like water pipes. When the switch is off, it is holding back all the pressure from the battery, so that pressure is high. When you turn the key on, that valve is open, and anything downpipe that consumes any electricity at all becomes a release of pressure, so the pressure drops.

Thanks. Brad.
(937)545-8991

May have float charger attached or recently connected and a surface charge is present. Could crank eng over a few seconds to remove any surface charge.

Need to know how much current is being drawn thru the switch with switch ON. The more current being drawn will make the voltage drop (VD) increase across the ign switch. Once you know the current, divide the VD by the current and get the resistance on the ign switch. For example; if VD across switch is 1.5V and current is 2 amps, that would mean ign switch resistance is 0.75 ohms.

Not sure what the spec is for your switch, but you could try contacting the manuf for that data. IMHO, 1 ohm or less should be fine.

Yes good catch guys, I do have my Noco float charger plugged in. I remember last summer while running the boat however, that my voltage gauge down in the cabin was 1- 1.5V higher than the dash was reading. And when hooking up a scanner, the voltage the engine was running at was also higher, matching the cabin pretty closely.

I'll have to do some more testing around the switch.

Easiest way to check for voltage drop across any component is put your voltmeter on the "in" (in your case the battery side normally red wire) and the "out" (in your case the stuff behind the dash and ignition, normally purple wire)

With switch off you should be reading full battery voltage. Switch on should normally be very close to 0.
1.5V would be a lot.