Electrical problem of the day

[SkunkBoat]

noticed that all three of my cabin lights were not working. Cabin & Head domes and the reading lamp.
The cabin dome has a Frankensteined toggle switch in it because ...well, because....
Thought that might be shorting to ground and popping the fuse.

Checked the fuse, looked OK. Blue &Green wire connector looked good. Swapped position on the fuse panel for shtzengiggles. No help.
Measured bulbs, 1 ohm eack...OK.
Measured volts in bulb sockets. Here's where it got strange. seemed to be low volts but climbed to 13+. I've been in this rodeo before. Thats a sign of a bad connection gremlin.
The fuse panel is fairly new. The connector there looks good. I found the blue/green wire in a bundle and traced it to one of the big white molex cable connectors. Pins were visibly green.
Pulled the connector apart and sprayed liberally with contact cleaner. I have LIGHTS!

Now all three fixtures are dangling while I surf amazon for possible LED replacements or maybe just LED bulbs

The perko dome light switch is about $20.

 

[Chutch]

noticed that all three of my cabin lights were not working. Cabin & Head domes and the reading lamp.
The cabin dome has a Frankensteined toggle switch in it because ...well, because....
Thought that might be shorting to ground and popping the fuse.

Checked the fuse, looked OK. Blue &Green wire connector looked good. Swapped position on the fuse panel for shtzengiggles. No help.
Measured bulbs, 1 ohm eack...OK.
Measured volts in bulb sockets. Here's where it got strange. seemed to be low volts but climbed to 13+. I've been in this rodeo before. Thats a sign of a bad connection gremlin.
The fuse panel is fairly new. The connector there looks good. I found the blue/green wire in a bundle and traced it to one of the big white molex cable connectors. Pins were visibly green.
Pulled the connector apart and sprayed liberally with contact cleaner. I have LIGHTS!

Now all three fixtures are dangling while I surf amazon for possible LED replacements or maybe just LED bulbs

The perko dome light switch is about $20.


View attachment 33466

I replace all my interior light bulbs with a led version with the same pin config and they work well.

 

[dogdoc]

I went with bulbs

 

[seasick]

The high voltage is measured wit the fixture n the ON state would indicate a bad ground.

 

[SkunkBoat]

The high voltage is measured wit the fixture n the ON state would indicate a bad ground.

That would/might be true if I had the ground of my meter on a known good ground like a terminal board and I was measuring just the Pos wire of the fixture. But I was measuring from the black wire of the fixture to the blue/green wire of the fixture.
The reading will be diffent depending on how many bulbs are still in the circuit.
The fixtures are in parallel to each other but in series with the bad connection.

What happened was that the corroded pin in the connector had more resistance than the bulb circuits. The bulbs are 1ohm. @ 12V they would carry 83mA and burn 12W.
When the bulbs are in place, allowing curent to flow, most of the voltage is dropped across the bad connection. That would dissipated as heat. there is much less current than normal because of the bad connection in series. The connector has to carry the current for all three bulbs. The bulbs don't have enough current to light.
My meter has very high resistance, in the megohms. It can read the voltage even though very little current is flowing.
If the bulb(s) were there, it would not read 13V.

 

[DennisG01]

I went with bulbs

That's probably a good idea. I mean, if you stuck something else in there, like hot dogs, it probably wouldn't work so well

 

[SkunkBoat]

I've seem similar problems caused by bad crimps of butt connectors, loose screws on terminals, and most often, anywhere that has green corrosion (vertigris).
ATO fuses and fuse holders/fuse panels are a major source of gremlins. The vertigris is hidden...

 

[seasick]

Try a test lamp with an incandescent bulb and see if it lights when the test tip is touched to the 12 feed lead. Then move along to the terminal f the lamp and see if it lights.
Bad grounds are tough to isolate using a DVM.

 

[SkunkBoat]

Try a test lamp with an incandescent bulb and see if it lights when the test tip is touched to the 12 feed lead. Then move along to the terminal f the lamp and see if it lights.
Bad grounds are tough to isolate using a DVM.

If i suspect a ground I just grab a long piece of 10awg THHN from my shed and I can test with a known good ground anywhere on the boat. Simple

 

[SkunkBoat]

So, after getting it to work, I then had to deal with a BS replacement switch in one fixture and then a nearly broken off wire on the lamp socket of the other fixture (because they were dangling during troubleshooting..
Bought new Perko mini switch. installed. No light again.

Looked back at the plug again. This pin below was still hanging on by a wisker until I tugged on it.

I spliced the wires around the plug to get me going.
Been a long time since I did molex pin replacement. Need the tools.

 

[enfish]

So, after getting it to work, I then had to deal with a BS replacement switch in one fixture and then a nearly broken off wire on the lamp socket of the other fixture (because they were dangling during troubleshooting..
Bought new Perko mini switch. installed. No light again.

Looked back at the plug again. This pin below was still hanging on by a wisker until I tugged on it.

I spliced the wires around the plug to get me going.
Been a long time since I did molex pin replacement. Need the tools.


View attachment 33517

I might be tempted to redo the whole thing and replace it with connectors that are more water tight... but knowing me, that project could snowball quickly and turn into rewiring the entire boat...

 

[SkunkBoat]

I will not repin any of these connectors. They have not been apart in 24 years. They only exist to make building the boat easier.
When I find another problem it will get hardwired around the plug.

 

[Fishtales]

Wiring ghosts always suk. I really hope GW does a better job today than the past in the wiring department.