weak lights in bilge

[skipper724]

I have two lights in my engine room. They are both very dim. One was flashing for a while but now dim. What could be the problem. I looked for loose or corroded wires. Found nothing.

 

[Max Simmons]

One of the best improvements I've done was to replace all the engine room lights with new LED's and add a few more to previously dim spaces. Are yours's LED? The old lights were 12v fluorescents and behaved as you described at times.

 

[Marco Flamingo]

I just finished my engine room light project. I also had just two really weak lights (although they had been upgraded to halogen), which explains why the PO had three 120v trouble lights onboard. I checked the original lights to make sure that I had +12v (even though the lights seemed dim), then spliced into the wires with very thin wire (20g). I ran this though Legrand Cordmate stick-on surface conduit around the inside rim of my hatches. In 4 places I spliced in cheap LED stick-on light sticks in parallel using PosiLocks. The stick-on stuff requires a clean non-greasy surface, so might not work in all engine rooms. A $25 project and one hour wearing knee pads.

I turned off the original lights, as they now add nothing but use 10x the electricity of all my new LED lights according to my battery monitor. Checking oil, changing oil, filter changes, generator issues, all can be done in good light without a head lamp or trouble light. Even finding that screw that I always drop.

 

[skipper724]

One of the best improvements I've done was to replace all the engine room lights with new LED's and add a few more to previously dim spaces. Are yours's LED? The old lights were 12v fluorescents and behaved as you described at times.

I had already changed to LED. Don’t know why they are dim. Put a meter on the and only get approximately 7 volts

 

[rgano]

I had already changed to LED. Don’t know why they are dim. Put a meter on the and only get approximately 7 volts

Well, there ya go, a bad connection upstream some place. Have fun finding it.

 

[Alaskaflyer]

Now that you know you have low voltage in the circuit you can use a voltage drop measurement technique to try to isolate the problem by working from connection point to connection point. One might suspect a corroded connection, even one that might not immediately appear corroded at a glance. Google it, plenty of automotive and boating articles explain how to do this.

Easy to do with a multimeter though as a practical matter when tracing wiring that runs at length, you need to have longer-than-usual test probe leads than those that typically come with a consumer-grade multimeter. You can order them on Amazon etc. I have a set of 10 foot test leads for mine.

 

[Comodave]

Well 7 volts is a problem. Usually replacing incandescent bulbs with LEDs doesn’t cause low voltage since LEDs draw so much less current. So it probably isn’t the size of the wiring causing the problem. It is probably a loose or corroded connection somewhere. Good luck finding it. Start at the panel and check the voltage and work your way to the LED lights checking the voltage as you go. Don’t just look at them and assume that because they look good they are good, confirm the voltage and then move to the next connection.

 

[C lectric]

Just for the heck of it I googled Vdrop and came up with what looks like a good source. It explains Vdrop and how to check for it.

https://www.hagerty.com/media/maintenance-and-tech/measuring-voltage-drop/

Read it.
I have typed this many times but this is easier.

I will mention specifically that the terminals where the crimp is made can also get corrosion inside that crimp barrel.

Last is do not just LOOK at the connections. Measure for Vdrop and take them apart and CLEAN the connections. Oxides can form that you can't easily see. Oxides create resistance which opposed current flow which creates Vdrop.

 

[FF]

Many times DC switches die , so if the voltage to the lamp is OK, it could be the switch. Cole Hersey makes good switches.

 

[Marco Flamingo]

Trace possible voltage drop starting at the circuit breaker. If you are lucky, it is a bad connection that is accessible at the breaker or buss bar. You may find that the circuit that runs your engine room lights is soon sandwiched between the engine room ceiling and the cabin floor with the wires fastened such that it can't be pulled (with a chaser string) to allow you to fish another pair of wires back in. Also, the lights would have parallel connectors sandwiched in and replacing the wire is likely impossible. There, your only fix is to use wires running across the ER ceiling using conduit.

I had low voltage (3.5V) on my port V berth bulkhead light. All other lights in the forward cabin circuit had full voltage. It had to be a bad connector behind that light, but I found out that the light circuit had been built into the bulkhead prior to it being fiberglassed on both sides. In fact, where the fixture electrical leads exited the bulkhead, there was polyester resin encasing the wires. No way to pull, splice, etc. I had to run exterior conduit. I found a spot where the wiring daylighted (in a cupboard in the head), spliced in, and ran that back through the V berth bulkhead. Since I was running surface conduit, I ran it for two light (his/hers) on the bulkhead.

Here is the conduit prior to a finishing "T" connector above the light. This conduit sticks fine to gel coat. It would have to be mechanically fastened to ER insulation.