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Old 04-02-2011, 20:15   #1
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Which Is Red, Which Is Black ?

Hey All,

I'm trying to replace a fixture on my boat...and I dont want to burn anything up/out. On this light fixture, which terminal connects to positive and which connects to negative...or does it not matter. Although the picture isn't that great, take my word for it...both the wire ends are exactly the same with red attachment and a blade connector....why they did this, I have no idea, but its lame.

Also, is there any possibility of ruining the fixture if I installed it backwards???

Sorry for the noob question...electrical confuses me.

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Old 04-02-2011, 20:17   #2
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Most of these don't care which wire connects to which, most of the time. Just strip off the ends of your feed and before you attach the connectors, hold them against the lights wiring with the switch on. That will tell you. I have a couple of wires with alligator clips on both ends to do testing like this. Chuck
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Old 04-02-2011, 20:18   #3
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If it's an incandescent, it won't matter.
If it is being replaced with an LED type fixture, every one I've ever seen has a built in reverse polarity diode.
That means if you hook it up backwards, nothing happens.
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Old 04-02-2011, 20:20   #4
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I dont get it then

I've hooked it up to my wires...and nothing. I verified there is 13.4volts with my multimeter at the wires, at the blade connectors...but nothing powers on.

How can I test if the bulb is bad? I've also tested with a whole bunch of other bulbs, but I cant tell if they're bad or not either (box of old spares).
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Old 04-02-2011, 20:21   #5
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Quote:
Originally Posted by senormechanico View Post
If it's an incandescent, it won't matter.
If it is being replaced with an LED type fixture, every one I've ever seen has a built in reverse polarity diode.
That means if you hook it up backwards, nothing happens.

Exactly
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Old 04-02-2011, 20:26   #6
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Besides the polarity, LEDs also need a specific voltage to work. If this is a 12V LED good, if not, you may have fried the LED.

Try reversing the polarity, and (I know this is silly) check to make sure the fizture isn't turned off.
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Old 04-02-2011, 20:27   #7
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Quote:
Originally Posted by night0wl View Post
I dont get it then

I've hooked it up to my wires...and nothing. I verified there is 13.4volts with my multimeter at the wires, at the blade connectors...but nothing powers on.

How can I test if the bulb is bad? I've also tested with a whole bunch of other bulbs, but I cant tell if they're bad or not either (box of old spares).
turn your meter to the OHM selection, and measure across the terminals on the bulb, if you see and infinite resistance the bulbs are bad, if you see close to 0 your bulbs are good. If you're checking LED's you need to check the leads in both directions on the diode check setting. The reading will be in volts instead of ohms.
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Old 04-02-2011, 20:29   #8
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Since the light itself is a diode current only flows in one direction.

Using an ohmmeter, connected one way shows an open, connecting the other way shows a short, or nearly so.

Also, take it straight to a battery and touch it to the connections both ways, if don't light up it's bad.

You won't hurt it hooked up backwards.
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Old 04-02-2011, 20:30   #9
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in laymans terms if it is a led light change the wires over,pos to neg and neg to pos and if it still doent work then the thing is dud.
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Old 04-02-2011, 20:31   #10
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This is an incandescent bulb and fixture

When I test the bulbs, I set my multimeter to ohms (the omega symbol), my bulb are reading 2.1...for 4 of the bulbs I have.

That is not near zero, nor is it infinite..what does that mean?
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Old 04-02-2011, 20:33   #11
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Blubs are good

How are you with pumps and valves? I ask because electricity works a lot like water in a pipe.
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Old 04-02-2011, 20:35   #12
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2.1 is near zero, rather nearer to zero than 1000 Ohm
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Old 04-02-2011, 20:36   #13
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Quote:
Originally Posted by night0wl View Post
This is an incandescent bulb and fixture

When I test the bulbs, I set my multimeter to ohms (the omega symbol), my bulb are reading 2.1...for 4 of the bulbs I have.

That is not near zero, nor is it infinite..what does that mean?
If that is 2.1 ohms and not on the kila or mega setting then that would be about right for an incandescent bulb.

Go to the battery. Just because you read 12V at the wires does not mean you have a good connection. If you have a corroded connection leading to that wire it could show 12V with nothing attached but as soon as you connect a load (like a light bulb) the corroded connection will not let enough current flow to work. If you have four or five hands you can connect the voltmeter and light to the wires at the same time and see if you still get 12V or if it drops. Or you could just connect it straight to the battery to prove that the light itself is good then mess with the wires.
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Old 04-02-2011, 20:37   #14
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Blubs are good

How are you with pumps and valves? I ask because electricity works a lot like water in a pipe.
All other pumps, valves and light fixtures seem to work. Whats strange is that the old fixture broke and the BRAND NEW one I got from Beneteau doesn't seem to work either. Just too much coincidence. I have to be doing something wrong

The odds of two fixtures being bad are just too rare.

Any other way to test???
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Old 04-02-2011, 20:39   #15
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That is the reading expected. Check the wires are correctly crimped to the connectors.
Check the switch is working. Check the wire connecting in the base.

That is all
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