Electrical gremlin - Is this even possible?

[Soleares]

This is my first post on this forum. I have been reading it avidly for a few weeks now that I bought my first boat; this forum is a treasure trove! My punch-list on my 2003 H356 is getting shorter now that the safety issues have been addressed, and the info posted here has been very, very helpful in fixing the issues properly.

Here's the Mystery:
The salon lights (12V halogens, with individual toggle switches) won't work. All four of them! These four lights with individual switches, and another 6 or so without switches, are all connected to the same breaker. The lights without switches work just fine. The defective lights are getting power.

The defective lights are wired in parallel according to my manual. I measured 12 volts at the wires in the headliner where the lamps are connected to the circuit, so all of the fixtures are getting power. The bulbs all test good )although one fixture is missing a bulb). So by process of elimination that means that something in the fixture itself is broken, either the toggle switches or the mounting bases. How is it possible for ALL 4 fixtures to fail at the same time?!

I had the marina crew have a look, after I was baffled by this, and they have no idea how this could happen either. The marina owner even called the PO, who stated that 3 of the 4 lights in question worked fine prior to the sale.

I guess the next step is to replace one of the complete light housings and see if this works. Any help in suggesting a possible cause or next step would be appreciated.

 

[Don12364]

Assuming the bulbs are okay look closely at the lamps themselves. They may have a switch incorporated where you press the glass dome or turn it etc.
Just a thought

 

[Soleares]

Thanks, I'll check that out as well when I go to the boat tonight.

 

[redunculous]

Can you also get your voltmeter and confirm powers running through the switch?

 

[cwkemp]

Soleares,
If the fixtures test good you could be looking for a bad connection to that branch of the circuit which might allow a test reading of 12v without load but not permit enough power to light the halogen fixtures, but test your fixtures first. You could also plug a known good fixture (or 12v test light) in place of one of the switched lights. Then I would proceed by disconnecting a fixture and testing its switch looking for continuity in the closed (on) position. If the fixtures connect to the supply wiring using some sort of socket or plug, I would check for physical damage or oxidation there as well as the bulb sockets themselves. Past that I'd need more detailed info on the fixtures and circuit. The fact that all 4 failed could just be coincidence. Keep us posted, and welcome.
Clint

 

[Jake N Eggs]

Check that the negative is connected to the ground circuit. This is assuming that you checked the positive at a common ground. You can also check the voltage between the two wires going to each fixture. If you have voltage between the two wires the problem must be in the fixture. If there is no voltage then it must be a ground circuit problem.

 

[Steve Dion]

I would check the connection to that first switched light. I think I remember having a similar problem on my H'31 many years ago and it was the connection on the circuit.

 

[Bill Roosa]

Check the ground wire. If they are wired in parallel then the grounds probably are too. When you checked the voltage available did you use the ground wire or a wire to another ground? If it is broken and wired in parallel the it would cause all of them to stop working at the same time.

 

[Ken13559]

Soleares, I believe it is the switch problem. Its a small switch and the conducting plate inside has slight oxidation/dirt. I've several of this lighting assembly and only 1 always has this problem even after I dismantled the switch to clear the conducting plate afew times. So I replaced the switch with similar one but different brand and have no problem after that. Strangely the others are working fine. So if you can, change the switch to same size but different make.

 

[Forrest15112]

A couple of things come to my mind, first, don't be offended, but are the fixtures of the type that twist on and off? My boat has these types. There is one switch for all cabin lights and each can be turned off by twisting the fixture. The other thing is these same fixtures' electrical connections are just stripped wires that are pinched between a brass tab and the plastic housing. Not very good connection when fresh and porperly done. I had to re-do all of these as the exposed wire wasn't tinned and oxidized, and during a long setup, moisture had added some corrosion. Check for voltage at the terminals where the bulbs plug in. It sounded from your description that you checked the line feeding it. If you don't have full voltage, you have a faulty or oxidized connection. I would inspect/ replace all of the connections. If you have some minor oxidation on terminals, a pencil eraser does an ok job removing it.

 

[Soleares]

Thanks everyone for your help! I did my homework today and swapped out a known good light for one of the defective ones, and it worked okay. Then I disassembled the defective one and tested the connections with the multi-meter and found that the switch was indeed bad. My hypothesis now is that all four switches experienced the same failure mode, oxidation from sitting for years on an unused boat. I guess I am in the market for four new 2.5" fixtures! I wouldn't mind upgrading to some chrome numbers instead of el cheapo plastic ones I currently have.