Electrical Draw draining cranking battery

[WestTexasRanger]

I recently started having problems with my cranking battery going dead.

The only electrical changes that I’ve made recently are replacing my tachometer with a Level 1 MercMonitor and adding a separate float switch (Rule 40A Rule-A-Matic Plus) to my existing Rule manual bilge pump.

Using a digital voltmeter connected directly to the battery and the ignition key “off”, you can see the voltage drop .01 Volts every 90 seconds or so. That doesn’t sound like much but it adds up pretty quick.

Since the float switch is connected directly to the battery, I started there. I removed the in-line fuse from the battery positive to the switch, and Voila, the voltage stopped dropping. Problem solved, except that a float switch without a fuse is pretty much useless.

My question: Why is the float switch causing a draw on the battery, even though the bilge pump isn’t running?

I’ve included the wiring schematic showing how the float switch is wired. This was how it was recommended that I wire everything so that I have both automatic operation (via the float switch) or a manual override (via the switch at the console).

[CatFan]

The likely (and only probable) answer is that the float switch is on and sending power to the pump and the pump is running. They can be pretty quiet when dry.

Switch your meter to DC Amps and switch the leads accordingly. With the fuse for the float switch removed, put the leads on each side of the fuse holder. Measure current as is, then move the float switch to activate it and see how the current changes.

What bilge pump and float switch do you have?

[WestTexasRanger]

Rule 40A Rule-A-Matic Plus float switch

Rule 800 20DA manual bilge pump

[WestTexasRanger]

Pump is definitely not running. I’ll check to see if there’s any current draw in the morning.

[billnorman1]

Check for 12 volts or so on the positive pump lead. Any voltage indicates the switch is feeding through. Is it a float switch or a water sensing switch? If it's a real (micro) switch no volts should come through.
Also, even if it shows no volts to the motor, it can have feed through and the motor not run because it isn't enough volt amps to start the rotor, which will knock any small feed through down to zero due to the locked rotor effect.
Although it's hard to prove with readings except milliampere readings on the input to the switch, it looks like the switch has some feed through and if your problems started when you put it in, it doesn't work for you. I'd go with a switch type versus a moisture sensing type.

[WestTexasRanger]

It’s a micro-switch, not moisture sensing. Will be conducting some more tests shorter and will report my findings.

[WestTexasRanger]

I found the source of what was discharging my cranking battery and it wasn’t related to the newly installed bilge switch.

The power drain was from two recently installed Garmin EchoMap units and the use of the boat’s battery cut-off switch. I’ve never used a cut-off switch (despite many of my boats having one) in my 45+ years of boat ownership and am not sure why I started on this boat. Anyway, every time I turned the cut-off switch to “on”, the Garmin units were powering up. Since they have covers on them, I was unaware that they were “on”, until I saw a glow emanating from around one of the covers last night. I turned the units “off”, turned the cut-off to “off”, then switched the cut-off to “on”. Both of the Garmin powered up.

I’ll need to keep an eye on this in the future or see if the EchoMaps have a feature that only allows them to be turned “on” manually, instead of automatically when they since power. I can always connect them to an accessory switch.

Thanks to everyone who replied!

[haus9393]

I found the source of what was discharging my cranking battery and it wasn’t related to the newly installed bilge switch.

The power drain was from two recently installed Garmin EchoMap units and the use of the boat’s battery cut-off switch. I’ve never used a cut-off switch (despite many of my boats having one) in my 45+ years of boat ownership and am not sure why I started on this boat. Anyway, every time I turned the cut-off switch to “on”, the Garmin units were powering up. Since they have covers on them, I was unaware that they were “on”, until I saw a glow emanating from around one of the covers last night. I turned the units “off”, turned the cut-off to “off”, then switched the cut-off to “on”. Both of the Garmin powered up.

I’ll need to keep an eye on this in the future or see if the EchoMaps have a feature that only allows them to be turned “on” manually, instead of automatically when they since power. I can always connect them to an accessory switch.

Thanks to everyone who replied!

yes all Garmin units power up when power is applied to a circuit. I have this happen on my 1022 and livescope when I turn on my cutoff switch. I rarely turn my cutoff off unless the boat is going to sit for a long period. Not sure if you can disable this feature.

[billnorman1]

That's good to know. Good to know, but not necessarily a good feature to have.

[Lowerider58]

There is a setting on the Garmin units that will disable the auto on feature.
I'm not near my boat right now to tell you exactly how to do it but it’s in the settings. Check your Garmin manual or look around in the settings.

[ifishinxs]

Auto on is the default setting on the Garmins. You can turn this feature off the in menu settings. I installed a switch at the console so that I can turn my MFD’s on and off with the switch.