10 watt 12 volt system

[sparky1118]

I have a customer who has low voltage lighting going down their dock. Every year before they come back for the season I always swing by and make sure the lighting is working for them. This year I had one dock light that wasn’t working. I changed the bi pin bulb and still nothing. Removed the bulb and wirenuts and tested for voltage and I had my 10 volts. Got another bulb just in case I had a dud and still not working. Here is where it gets funky. I tested for voltage while the bulb was in the socket and voltage was zero. Removed the bulb and voltage went back up to 10 volts.... figuring there was an issue with the socket I tested each one of the leads to ground and no issues. Tested continuity with bulb in and I had it. Removed the bulb and didn’t have it. So I ruled out the fixture. Now the wire goes straight back to the transformer no other lights on this leg. So I pushed the bi pins directly into the wire and voltage dropped down to zero again. I’m wondering if I have a break in the line. And I have voltage when no load is on it but as soon as something is drawing from the line it can’t handle the load. I have no idea I’m out of ideas.


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[ptonsparky]

Check the line side voltage of your transformer. Transformers do fail.

Back when I was young the radio on our cars would work for quite a while when parked and engine off. Throw the starter load on and everything would go quiet. Let up on the switch and the radio would come back on, maybe. That’s when you we’re glade you parked at the top of the hill and had a stick shift.

 

[ptonsparky]

Does this wire go underground any distance?

What meter are you using? Do you have a megger yet?

Remove the wires from the transformer. Short them. Go to other end and measure Resistance.

Sorry, I just noticed this was the only lamp not working.

 

[sparky1118]

This is a multi tap transformer there are other lights that are on it. They are all functioning properly. The low voltage line does not go underground it is secured to the side of the dock


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[hbiss]

So, we have voltage at the socket until you put a load on it. That would indicate a high resistance open someplace, probably from corrosion. If the wiring run is just secured to the dock I would just plan on replacing it unless you can see something obvious.

-Hal

 

[sparky1118]

So, we have voltage at the socket until you put a load on it. That would indicate a high resistance open someplace, probably from corrosion. If the wiring run is just secured to the dock I would just plan on replacing it unless you can see something obvious.

-Hal

That is my next move thank you


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