Instrument panel clicking, dropping voltage

[chille51]

So this afternoon I was wiring up my new trim tabs, and looking for a place to pull a connection to the ignition switch for the auto retract. So I turned the key on to aux power and started to work with the multimeter - when I noticed a distinct "click" sound, accompanied by approximately a .5-1V drop on the multimeter. It it is a mechanical click - sounds almost like a relay, but there aren't any relays in my panel. It kept happening every 30 seconds or so - click and voltage drop for a few seconds, then another click and back to full power. This was before I hooked up the tabs - so I hadn't altered anything yet.

I poked around and put my ears up behind the panel and I am pretty sure it is coming from the tach, or the hour meter that is built into it. It is an old Honda needle tach with the analog dials hour meter. My instrument panel is very basic - tach, speedometer (that is not hooked up), gas gauge, and voltage meter. That's it, all analog. Motor is a Honda 75hp 4 stroke, probably 1998 by the serial number.

Any ideas what this might be? I suspect the hour meter, but not sure why the voltage drop. Also not sure if it is a problem or not - I rarely am sitting with the key in the aux position. I usually just get in and fire up the motor. If I am trolling I am on the kicker and key is off. I might turn it on for a couple seconds once in a while to read the fuel gauge but that's it. Its possible this click has always been there and I just never noticed before.

 

[Alex_c]

Could be the hour meter uses a solenoid to advance, which would explain the clicking. The voltage drop could be a result of high resistance due to corroded power wires or connections.

 

[chille51]

Could be the hour meter uses a solenoid to advance, which would explain the clicking. The voltage drop could be a result of high resistance due to corroded power wires or connections.

Could be, but why would the hour meter click steadily every 30 seconds or so when I don't even have the motor running? It shouldn't even be trying to advance at that point.

Corrosion is a real possibility. I rewired all of my accessories last year with all new wire, vertex connectors, Blue Seas panels, dual battery setup etc., but left the motor wires to the controls and the instruments alone. Everything was working and I didn't wanna mess with it. Sounds like its time to at least give the connections a clean.

I'll start there - unplug the tach for a few minutes to confirm that is the source, then clean up all the connections and see where I am at.

Other ideas welcome in the meantime.

 

[Alex_c]

Some hour meters run when they have power, some run off a signal from the tach. Not sure how yours operates, but it seems like something is turning on intermittently. Could also be a wire shorting to ground and arcing, but I doubt it would do that without physically jiggling the wires