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Old 01-14-2022, 02:28 PM   #1
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Why is this light fixture switched on ground?

Can someone explain why the ground side is switched on this fixture? New fixture I installed also has the ground switched. Shouldn't the positive (red) side be switched as a best practice?
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Old 01-14-2022, 03:16 PM   #2
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Not sure the switch location matters....just the overcurrent protection.
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Old 01-14-2022, 04:04 PM   #3
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A lot of lights donít follow the common color code. Who knows?
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Old Yesterday, 10:05 PM   #4
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Yes, positive should be the switched leg. But as they say, electricity doesn't know what color the wires are, so the wire may have been reversed somewhere. Don't rely on what it "should" be; use a multimeter to verify which leg is positive.


If both wires are black, standard practice is to have some marking such as writing or ribbing that indicates the ground or neutral wire. Most sparkies will rely on the microscopic writing on the wire's insulation as the indicator. But when it comes to electricity, don't trust. Verify.
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Old Yesterday, 10:53 PM   #5
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Quote:
Originally Posted by jhance View Post
Can someone explain why the ground side is switched on this fixture? New fixture I installed also has the ground switched. Shouldn't the positive (red) side be switched as a best practice?
You are not showing all connections, all wires. I do not see a red wire, just a red connector. The light is wired like most, it is up to the installer to know which wire to connect the positive and negative or hot & neutral with AC
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Old Today, 07:29 AM   #6
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"Why is this light fixture switched on ground?"

Because it wont kill you on low voltage , do it with 120v or 240v and you could die.
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Old Today, 09:25 AM   #7
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On DC lights in boats....many are daisy chained so it doesn't really matter where the switch is or pos/neg connections.
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Old Today, 12:29 PM   #8
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All true about low-voltage DC and high-voltage AC. Still recommend using wiring best practices rather than "hey, stuff works, who cares." Color coding provides guidance and safety for the next guy who comes along and has to work with the circuit. For example, if you have a parasitic load before the switch rather than after, it's tougher to troubleshoot which circuit has it and how to fix it.

You don't have to do a whole-boat rip-and-rewire but if you find something that either wasn't installed per code/ guidelines or was modified incorrectly by a previous owner, see what you can do to put it in proper shape.
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Old Today, 01:37 PM   #9
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I see you have a Camano Troll. On our 2005 Camano I replaced all the cabin light bulbs with LED's. The lights did not work. I found the fixtures were wired with positive to the base of the bulb instead of negative to the base. Swapped the wires and everything worked.
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Old Today, 01:53 PM   #10
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The wiring for daisy chained light in older boats....there is no positive or negative until hooked up... I have seen different fixtures in line wired alternately because it didn't matter for DC, incandescent bulbs...and it didn't matter where you broke or made the circuit.

Best practice???? No..but it DIDN'T matter in the big scheme of things and I would bet good money nobody got hurt or burned a boat down because of this.

Do it better if rewiring... if replacing just a couple fixtures or switches...man I wouldn't sweat it.
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Old Today, 03:17 PM   #11
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I have replaced two lights that look to be original from the manufacturer. Both lights were switched on the negative leg (switch attached to the black boat wiring). There must have been a reason for this, I would think, so I just replaced the lights as they were installed. But new lights have this same phenomenon. Why are black wires coming into and out of the switch on the light fixture if you are supposed to switch the positive (red) side? Black to black, red to red, right?

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The wiring for daisy chained light in older boats....there is no positive or negative until hooked up... I have seen different fixtures in line wired alternately because it didn't matter for DC, incandescent bulbs...and it didn't matter where you broke or made the circuit.

Best practice???? No..but it DIDN'T matter in the big scheme of things and I would bet good money nobody got hurt or burned a boat down because of this.

Do it better if rewiring... if replacing just a couple fixtures or switches...man I wouldn't sweat it.
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Old Today, 04:30 PM   #12
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Do the lights only have black wires and no red wire?

The positive lead should be switched. It is preferred to be colored red on a 12v DC circuit. The light may not have a positive or negative side so it has 2 black leads and doesn't care what gets connected to where, unless the leads are polarized and both black then the positive lead will have writing and or white hash marks on it.

Always test and verify. I may use a 4 conductor cable to run two 12v DC circuits. One is red +, black - and the other may be white +, green - with the darker color of the pair negative. Depends what you are doing and what you have available.
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Old Today, 07:02 PM   #13
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This is the new fixture. I understand that the positive side is generally the side you want to switch, but that would mean I need to connect the red wire from the fixture to the black wire from the boat, and the black wire from the fixture to the blue wire from the boat. Everything in my being is telling me not to do that!

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Do the lights only have black wires and no red wire?

The positive lead should be switched. It is preferred to be colored red on a 12v DC circuit. The light may not have a positive or negative side so it has 2 black leads and doesn't care what gets connected to where, unless the leads are polarized and both black then the positive lead will have writing and or white hash marks on it.

Always test and verify. I may use a 4 conductor cable to run two 12v DC circuits. One is red +, black - and the other may be white +, green - with the darker color of the pair negative. Depends what you are doing and what you have available.
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Old Today, 07:17 PM   #14
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You really should have a Volt-Ohm meter (VOM) and measure out what is positive and what is negative.
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Old Today, 07:20 PM   #15
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Greetings,
Mr. j. I share your anality (word?). What I would do is re-colour the light wires. Buy some coloured heat shrink and apply as needed. Put some red on the black fixture wire and some black on the red..
https://www.walmart.com/ip/8-Sizes-P...3&gclsrc=3p.ds


Edit: Just read Mr. HT's excellent suggestion. Re-colour as to your discovery.
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Old Today, 07:47 PM   #16
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Once found an entire house wired by owner where neutral AC was switched. I was changing a light fixture when I got a charge out of it.

At the time I was told the owner worked with circuit boards which are always switched after to reduce arching. Is that true?
Perhaps a new hire came from same background when this boat was built
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