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Thread: Pool lights fail to come on with good power to the fixture

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    Pool lights fail to come on with good power to the fixture

    Lights in my pool are not working anymore. I have 12V (measured) feeding a Pentair submerged fixture. Took the bulb out and it had 0.3 ohms continuity. Measured the voltage in the socket and found 12V there as well. Took the bulb to the transformer and connected it directly to the 12V output and the light glowed brightly. But when I put the bulb back into the fixture, it doesn't light. Cleaned out the socket and the bulb to make sure contacts were good. I am at a loss. Any ideas?
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    Re: Pool lights fail to come on with good power to the fixtu

    You have voltage but what about current? What you see as not lighting might actually be a very dim glow that isn't perceptible in daylight. That would occur if partial continuity was lost in the wire or connections between the transformer and light. Nicked up wire, corrosion on connectors, or similar. You would still see full voltage even though the capacity to deliver the required current for the light was lost.
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    Mod Squad Bama Rambler's Avatar
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    Re: Pool lights fail to come on with good power to the fixtu

    Sounds like a bad termination breaking down under load. Find every connection in the wiring and disconnect, clean and reconnect it.
    Dave J. TFP Moderator
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    Re: Pool lights fail to come on with good power to the fixtu

    Since the light was bright at the transformer, I think the breakdown can only be at the junction box near the pool edge. I'll try to see if it lights at that location and if it does, then I'll cut the wires to get at new metal and then reconnect. I admit that those connections looked awfully corroded. Thanks for the advice. I'll get back to you this afternoon hopefully.
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    Re: Pool lights fail to come on with good power to the fixtu

    Cut all the wires and stripped the insulation. Tested the fixture with my meter and it had a resistance of 4.3 ohms with the bulb inserted. Connected the wires together with new connectors. Used steel wool on the interior of the socket and the base of the bulb as well. Tested the bulb right there at the junction box 2 feet from the edge of the pool. Then turned power on and no light. Used my meter at the junction box to confirm I still had 13V. Is there some type of safety device buried inside the epoxy that doesn't let the bulb turn on unless it is submerged in water???? I have one other light with the same symptoms and noticed that it is slightly different from the ones that are working. They both have this ground spring that pushes against the bulb when it is inserted. There is also some type of flexible plastic tube similar in size to a piece of chalk, sticking out of the epoxy along the edge of the aluminum cover. A small bit of it also appears to be barely sticking out at the bottom of the socket. I noticed that several of the fixtures had wildly varying resistance without the bulb inserted. Even negative resistance values were coming up. Could it be chemical deposits on the socket fittings making a pseudo battery? I teach a college course on analog and digital electronics, but I'm really learning about how practice and theory can be completely different things.
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    Mod Squad Bama Rambler's Avatar
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    Re: Pool lights fail to come on with good power to the fixtu

    The fact that the bulb worked right at the transformer tells you that it isn't anything in the bulb preventing it from lighting. If it doesn't work at the junction box keep working back toward the transformer. The wires may be cut or spliced underground (even though they're not supposed to be).
    Dave J. TFP Moderator
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    Re: Pool lights fail to come on with good power to the fixtu

    Corrosion. Even though I sanded the socket with sandpaper and steel wool, apparently that was not sufficient. Continuity checks between the end of the wire at the junction box and the socket showed highly variable readings. Once again chemical conduction. Finally I looked up on the internet on how to clean copper and used the recommended mixture of flour, salt and vinegar. Poured it into the socket and soaked it for an hour, then rinsed it out with water. Looked like new. Decided to soak the remaining fixtures as well to save having to pull the lights out when the pool is full of water. Fingers crossed. Thanks for the help!
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