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Thread: Troubleshooting bad nav light

  1. #1

    Default Troubleshooting bad nav light

    This has me stumped. Red/port light works, but green/starboard doesn't. For the green light, using a multimeter, when the bulb is out I get about 12 volts with one probe on each of contacts where the bulb fits into. When I put in the bulb and again check the contacts I get no voltage when I check the two contacts and the bulb doesn't light. On the red light, when the red light is on I get about 12 volts when I use the probes on the contacts where the bulb fits into. The bulb is good (checked continuity and checked that it worked elsewhere) and I sandpapered all contacts. Any ideas?

  2. #2
    Sponsor potbuilder's Avatar
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    is it making good contact with the mount/base itself ?? squeeze it together a bit.

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  3. #3

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    Good contact.

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    The reason you are not seeing the problem using a volt meter it is very high resistance and there for does not load down the circuit.

    You may have high resistance in the ground side or power side of the lamps.. Use a ohm meter to find your problems.

  5. #5
    Member breausaw's Avatar
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    You most definitely have a contact issue somewhere, eithe rat the switch or light fixture. Start at switch or fixture and make sure you have good voltage, should get 12.6 volts if the battery is fully charged. Look for any corrosion or loose terminal attachments, remove clean and re-attach terminals using dielectric grease. The wire is usually the last thing to go bad unless someone used automotive wiring or somehow the wire got damaged, if the lines are visible definitely run your hand along them and check for any visible signs of ware or damage. Checking continuity between both ends of the wire is usually a last resort if all else fails. Nav lights are pretty simple, all you have is a switch, two leads and a fixture; you’ll figure it out I'm sure.
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    Ohm test are garbage for detecting a weak circuit, you can get 0.0 ohms on a circuit that will not carry a load and you can see 12V ,as you are now, on a circuit that will not carry a load. The light bulb requires more power than the circuit can provide per the resistance/demand of the bulb, you have a bad wire or connection some place. Likely on the ground side, perhaps on the back of the light assembly itself. An easy way to determine which side of the circuit is the issue is to run an independent wire - ground or power - direct to a battery (+) or a good known ground (-), then swap sides.

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    I would just replace the fixture. I would bet that the connecter where the wire goes in with the set screw is bad.

  8. #8

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    Or you could take the easy out and just buy a new boat that would come with a new light.

  9. #9

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    I'll probably just buy a new fixture. Can't figure out why (power is on) I get voltage when the bulb is not in the fixture and I make contact (using multimeter set on volts) with the fixture contacts, but then I insert the known good bulb and then the contacts show no voltage. On the nav light fixture that works, I get voltage coming from the contacts regardless of whether the bulb is in the fixture or out of the fixture. So the fixture IS getting power, but when the bulb is put in it's like the fixture stops getting power. Thought that maybe putting the bulb in the fixture was somehow spreading the contacts too much and cutting off power, but I used the multimeter probes to spread the contacts apart (with the bulb removed) and power didn't go away. Seems simple as hell and that's what gets me.

  10. #10
    Member SusitnaAk's Avatar
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    I have seen many light troubles come from just a bad ground ,I had one that would burn out lights in rough water found rubbed hot that time.Pull the light, take it to a batt confirm that it works with couple wires. If I read right sounds like you have power there. if so, going too bad ground or bad light socket. If those two things are not it, than you have to work your way back to the switch. I still lean towards bad ground

  11. #11
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    Quote Originally Posted by skydiver View Post
    I'll probably just buy a new fixture. Can't figure out why (power is on) I get voltage when the bulb is not in the fixture and I make contact (using multimeter set on volts) with the fixture contacts, but then I insert the known good bulb and then the contacts show no voltage. On the nav light fixture that works, I get voltage coming from the contacts regardless of whether the bulb is in the fixture or out of the fixture. So the fixture IS getting power, but when the bulb is put in it's like the fixture stops getting power. Thought that maybe putting the bulb in the fixture was somehow spreading the contacts too much and cutting off power, but I used the multimeter probes to spread the contacts apart (with the bulb removed) and power didn't go away. Seems simple as hell and that's what gets me.

    See my post above.

  12. #12

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    .338WM. Got it. Will troubleshoot more tonight. Got a replacement nav light base that I'll install if I can't figure out the problem. Thanks for the info.

  13. #13

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    Turned on power to the nav lights yesterday, ready to troubleshoot, and the light that I couldn't get to come on came on. Go figure.

  14. #14
    Member JR2's Avatar
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    Hey you fixed it...
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  15. #15
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