Electrical Gremlin - strange faint noise

[smokey73]

While doing some cleaning of contacts to correct some voltage drop in my DC system I was about to leave my boat and heard a strange, very faint, intermittant whirring noise coming from somewhere in my boat near the electrical panel. It was very very quiet this morning when I was about to leave so it may have been there for a long time and I just haven't heard it. The wind piped up a little and it was no longer quiet enough to hear it above the background noise.

The DC ON/OFF switch was ON from the Battery. The DC main breaker on the panel was off. The only things getting power should have been the bilge pump and the memory power for my entertainment radio/CD player (the radio was off though). The sound would be off about 5 seconds or so and then on again for about 5 seconds. The bilge pump was not running (bilge was bone dry) and I do not have the kind of level switch that "samples" level electronically every few seconds to see of the bilge pump needs to run. The small shower sump was off and not running. The sound was much like a very small computer fan or something like that. For the life of me I can't think of what would be making that sound.

Any ideas? I will be going over to the boat as soon as we have another very quiet morning or evening to see if I can find the source.

 

[kloudie1]

Mud Daubers?

 

[Davidasailor26]

Prop or engine noise from a nearby boat being transmitted through the hull?

 

[JoeWhite]

If you are plugged in to shore power, your battery charger is on and its cooling fans are making this noise. This happens when the bearings are dry. If so replace the fans as overheated charger leads to additional problems.

 

[smokey73]

Mud Daubers?

Interesting theory. The location is near where there are three vents so that is a possible source. I'll check that out! Thanks for the out of the box thoughts.

 

[smokey73]

If you are plugged in to shore power, your battery charger is on and its cooling fans are making this noise. This happens when the bearings are dry. If so replace the fans as overheated charger leads to additional problems.

On a mooring and the battery charger is not on. However, I do have solar power with a Blue Sky Solar Boost 2512i(X)-HV MPPT controller. From the Blue Sky manual there does not appear to be a fan for this controller. It uses the front metal panel as a heat sink so this is probably not it, but thanks for the idea, it got me to the manual to check it ou.

 

[smokey73]

No boats operating or even nearby but it might be my prop turning in the current. Could be a prop turning on one of them but the closest boat is about 80 feet away. I know sound travels well in water. It was on and off though and I would think a shaft spinning would be consistent (in the short term) as the current doesn't start and stop on a regular short term basis. I'll check that when I get back to the boat. I can put the shaft in gear (I normally do though so it is probably in gear). Thanks for the suggestion.

 

[Rich Stidger]

When you hear it again, shut off the switches for the house and starting batteries. If you still hear the sound then you know the source is not on your boat. If you do still hear it, lift a house battery terminal and insert a DVM to measure low currents. You will see the draw from the entertainment radio which should be under 10mA. Check to see if the current increases or decreases in time with the noise. If constant, repeat this test with the starting battery. The starting battery will have a small draw for the alternator diode leakage - probably under 2-3 mA.
If you still hear the cycling noise with no changes in current from the house or starting batteries, I would start looking for an external sound. Or see a shrink or get earplugs.

 

[LloydB]

Maybe your inverter cooling fan now that you've got a better/worse connection to the DC voltages feeding it?

 

[smokey73]

Maybe your inverter cooling fan now that you've got a better/worse connection to the DC voltages feeding it?

No inverter installed

 

[smokey73]

When you hear it again, shut off the switches for the house and starting batteries. If you still hear the sound then you know the source is not on your boat. If you do still hear it, lift a house battery terminal and insert a DVM to measure low currents. You will see the draw from the entertainment radio which should be under 10mA. Check to see if the current increases or decreases in time with the noise. If constant, repeat this test with the starting battery. The starting battery will have a small draw for the alternator diode leakage - probably under 2-3 mA.
If you still hear the cycling noise with no changes in current from the house or starting batteries, I would start looking for an external sound. Or see a shrink or get earplugs.

@Rich Stidger , sounds like a plan. Problem is that it really is a faint noise so things have to be very quiet for me to hear it. I may get a stethascope from my daughter and see if I can narrow down the location.

 

[Stu Jackson]

I may get a stethascope from my daughter and see if I can narrow down the location.

Get a long shank screwdriver with a thick handle.
Good luck happy hunting.

 

[Morgan donor]

Nicro Solar vent fans?
Although thay make enough noise usually easy to ID. Maybe you got a good one?
Description sure sounds like a bilge pump cycling. Put your hand on the pump just to be sure.
Unplug the CD player or remove the disc. They sometimes get in a software funk.

 

[smokey73]

Nicro Solar vent fans?
Although thay make enough noise usually easy to ID. Maybe you got a good one?
Description sure sounds like a bilge pump cycling. Put your hand on the pump just to be sure.
Unplug the CD player or remove the disc. They sometimes get in a software funk.

I don't have a Nicro Solar vent (plan to install one though) The CD player is not powered up except for the memory but I'll check that one out. I'll check out the bilge pump but I don't think that its the source since its much louder but maybe its "locked" up and I'm hearing an electrical "hum". Thanks for the suggestions.