Lighting Puzzle

I am stumped and could use some help.

In our forward cabin on our 2005 Mainship 400 we have two overhead fluorescent lights, mounted in the headliner. Each of the light fixtures has a switch on the fixture itself but they are also tied together and run through a single Vimar wall switch.

The problem is that in both the on and off position of the wall switch there is power going to both fixtures all the time. I can still turn each light on or off at the fixture by using the fixture mounted switch.

I assumed the problem was in the wall switch, so I pulled it out and found continuity across the terminals with the wires still attached. With the wires off there is continuity in the on position but not the off position. So the wall switch works fine. I have a spare switch so just to be sure I replaced it, but the problem still persists.

Do you think there is some sort of short in the actual wiring between the switch and the light fixtures? A single hot wire leads into one terminal of the wall switch and two lead out from the other terminal, one to each fixture I'm assuming. So if the problem is between the wall switch and the fixtures why is it effecting both fixtures?

The wires run through a very tight channel in the bulkhead covered by a piece of trim that appears to be glued on then under the headliner. Getting to them is going to require extreme surgery.

Any ideas? Pic of the switch is attached.

So do the lights work? It is possible the power was run to the light and the switch leg runs from the lights to the switch. Only one leg of the power would run to the switch and then return to the light to complete the circuit. So to answer you question if the two wires had indeed shorted or are now making contact than the lights would always be one. No short here just the completion of the circuit.

You would need to disassemble one of the lights and see how it is wired.

Good Luck

Yes, and you may need to trace the wiring between the two lights to see how they are connected, as the power side does not appear to be originating from the wall switch.

Yes, both lights still work fine and I can turn them on or off independently of each other using their respective fixture mounted switches. The two fixtures do not appears to be wired together other than through the wall switch as there is only one wire coming into the wall switch and two going out.

I will pull the lights apart and see if I can find anything.

Is the light on with the switch disconnected??

Are you certain that is the correct switch?


I guess it is possible that you have a three way switch set up and the other switch has failed.

OK, it seems I'm starting to make a tiny bit of headway, but I'm still confused.

The fixtures appear to be wired together, there are two blue (+) and two yellow (-) wires leading into the starboard fixture and one each going to the port side. I found continuity between the fixtures as well.

On the wall switch, as pictured, there are three blue wires. two of them have continuity with one or the other light fixture. The other has no continuity with anything I could find and is not hot.

The lights stay on even with the wall switch disconnected.

When the stb side fixture is turned on at the fixture's switch there is continuity across the port fixture's switch even when it is turned off but the light turns off when I turn the switch off (????).

I surrendered. I just put it all back together and turn the lights on and off at the fixture. Odd that that switch worked when we bought the boat but then failed.

draw it on paper

Draw what you think the circuit looks like from your observations. It will make it easier to troubleshoot with that in hand and easier to share on the forum. Also it seems as though you might be making continuity measurements when power is still applied. Throw the circuit breaker to the off position at the breaker panel that makes both lights go out before making any continuity measurements.

Also never surrender! The more you poke at this the more that you will learn about your boat!

Yep, no surrender.

Boat electricity is like doing a cross word. It is annoyingly logical & really frustrating when you can't work it out.

You are the beneficiary of countless years of human evolution, not to mention a sizable monetary investment by the state to bring you to this peak of human achievement, you owe it to all of us to overcome a bunch of Chinese made coloured wires, and show them who is boss on your boat.

If you fail what hope is there for all of us.(nurse, time for another one of my blue pills)

Obviously the lights are not connected to the wall switch.


Bob

or a different wall switch.

That's the thing. They are connected to the wall switch. It worked fine for a few months, then stopped. I haven't changed anything at all, just put in a ton of trouble shooting.

I was checking continuity with power applied.

I'm usually good at this sort of thing, albeit slow, but this one has my head spinning.

Sounds like a short between the positive feed wire to the switch and one (or both) of the wires leading from the switch to the lights. Do they share a common path anywhere where they could rub? With power to the circuit off, check with an ohmmeter between the disconnected wall switch single feed wire and each of the wires to the lights. Make sure the switches on the lights are off.

"The lights stay on even with the wall switch disconnected"

Are you 100% sure you don't have a second wall mounted switch some where? That's what it sounds like to me. The lights worked fine till someone or some how that second switch got turned on.

I believe they a three-way circuit would require a different style switch.

mike66 said:

I believe they a three-way circuit would require a different style switch.

Click to expand...

Assuming there is not a problem somewhere then a three way sw. is the way it SHOULD BE DONE.

However, boats do seem to get some stupid wiring done and there could be a separate, independent switch as pointed out. Maybe the P.O. did it.
Hopefully another sw. is the case.

Keep looking.

mike66 said:

I believe they a three-way circuit would require a different style switch.

Click to expand...

Yes you're right. If that was a Vimar three way switch it would have another set of connection holes.

But that is not what I was talking about. Looking at the wiring going to that switch and based on how the wires are going to the lights from what the OP said, I'm wondering if there is another switch feeding the lights.

I don't think there is another switch, but it is possible. I've tried it with every switch I can find on and off, but perhaps I just haven't found the right combo.

Interestingly, I did find another clue. The head has the exact same set up (wall switch and fluorescent fixture with attached switch) except with only one light fixture. It started doing the exact same thing a few months ago, but then miraculously started working again last week in the Bahamas. Only difference from the master cabin lights is that when the wall switch was turned to the off position the light would dim a little bit.

The head switch and the master cabin switch back up to each other on opposite sides of the same bulkhead. The wires for the head light and the master cabin lights share the same channel in the wall. When i had the master cabin switch disconnected yesterday the head light wouldn't work at all. When I reinstalled the master cabin wall switch the head light started working again. I think maybe one of the three wires on the master cabin switch goes to the head. Probably the one that had no continuity with anything in the master cabin.

Capt.Bill11 said:

"The lights stay on even with the wall switch disconnected"

Are you 100% sure you don't have a second wall mounted switch some where? That's what it sounds like to me. The lights worked fine till someone or some how that second switch got turned on.

Click to expand...

Now it gets a little more complicated. It would seem the two white wires are the positive feed.... one going to the head and one coming into the switch from the supply breaker. The single blue must go to the cabin light. Perhaps there is a short. You need to do some connecting/disconnecting one wire at a time as well as getting voltage and resistance measurements to trace where everything goes. So get to it. Cup of coffee, and I'm sure it will get straightened out. It would be very helpful to find which wire is supplying voltage at the cabin fixture and seeing if that wire had continuity with one of the switch wires, or if it comes from somewhere else.

:Your not close to a famous TRIANGlE are you?

Have you removed the switch and tried touching the wires together in different combinations ?

jimbob said:

:Your not close to a famous TRIANGlE are you?

Click to expand...

What, Isosceles?

So any resolution to the problem yet?

Andy G said:

What, Isosceles?

Click to expand...

Well, it's certainly not RIGHT.

(insert rimshot here)