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Thread: troubleshooting pool light

  1. Back To Top    #1

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    troubleshooting pool light

    Hi everyone,

    Last time I posted my first numbers and had some crazy high CYA and I am now getting around to draining my pool. Drained about 90% of the water out and figured that this would be a good time to try to fix my non-functioning pool light.

    It did work for a short time after I bought this house in September, but sometime since then it has stopped working. The fixture or housing (not sure about the terminology) is a Pentair 120v. The bulb is a 120v 250w halogen.

    These are the things I have done already:
    • Checked circuit breakers[/*:m:1o4beo8t]
    • Checked GFCI[/*:m:1o4beo8t]
    • Replaced the switch (it was a little corroded at the contacts)[/*:m:1o4beo8t]
    • Changed bulb (the old bulb looked fine actually, just did it for completeness)[/*:m:1o4beo8t]


    It still does not work, and at this point I am kind of out of ideas. From searching the boards here it seems like a continuity test would be a good idea. I have easy access to the junction box by the pump. I do not have a multimeter yet, although I plan to pick one up.

    Is it possible that the fixture itself has gone out? Is this a common thing to have happen? The pool is roughly 6-7 years old.

    I am eager to refill the pool and get going w/ the BBB before the weather warms up here, but if I am going to need to call someone out to look at this, is it better if the pool is mostly drained for them to troubleshoot?

    I am willing to call someone, I just want to exhaust all of my options and be as informed as I can before I do. If the fixture itself needs to be replaced, I may just bite the bullet and have a full on LED setup installed. Again, does the installer need the pool drained to have access?

    Thanks in advance for all your advice!
    ~12k gallon in-ground pool, PebbleTec surface, sand filter, The Pool Cleaner (2WD)

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    Re: troubleshooting pool light

    Change the light. They aren't real expensive and are not worth compromising the safety of your pool.

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    JasonLion's Avatar
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    Re: troubleshooting pool light

    A lot of the troubleshooting steps can be done with the pool full, but there are a couple of things that require the pool to be drained to below the light niche.

    It is possible for the fixture to fail, though it is rather more common for there to be a problem with the wire between the fixture and the junction box.
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    Re: troubleshooting pool light

    Quote Originally Posted by simicrintz
    Change the light. They aren't real expensive and are not worth compromising the safety of your pool.
    Can you expand on this? I already changed the bulb. Are you referring to the fixture that the bulb screws into?
    ~12k gallon in-ground pool, PebbleTec surface, sand filter, The Pool Cleaner (2WD)

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    Re: troubleshooting pool light

    Quote Originally Posted by JasonLion
    A lot of the troubleshooting steps can be done with the pool full, but there are a couple of things that require the pool to be drained to below the light niche.

    It is possible for the fixture to fail, though it is rather more common for there to be a problem with the wire between the fixture and the junction box.
    Just to be clear, the troubleshooting steps I listed above I have *already* done. I currently have the pool drained out well below the fixture and am looking for next steps to take while the pool is drained.

    Thanks again
    ~12k gallon in-ground pool, PebbleTec surface, sand filter, The Pool Cleaner (2WD)

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    spishex's Avatar
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    Re: troubleshooting pool light

    Was there water inside the housing when you removed it? Once a fixture has been flooded inside and out for a while the whole thing can get corroded beyond repair. Whether the issue is the housing itself, or the wire between the housing and the junction box, you'd have to replace the entire thing either way.

    You need a meter first off. From there, check the incoming power at the junction box, and then either test for continuity on the light line (a 250W, 120v bulb should be about 55 ohms I think?) or remove the light and check for power on the light terminals. If you're able to get it working you'll also need to replace the lens gasket if you haven't done so already.

    If you end up having to replace the entire fixture as simicrintz suggested you'll need to know the cord length required to get from the pool to the junction box. This is the easiest solution and ensures that you've got a good, safe housing that won't require attention again anytime soon.

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    JasonLion's Avatar
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    Re: troubleshooting pool light

    The next step, which can be done with water in the pool, is to test continuity of the wire. There is presumably power at the circuit breaker panel, so the question is how far does it get from there. The most likely problems are between the junction box and the fixture, but there could also be a problem between the breaker panel and the junction box.

    If there is power at the junction box, and is not power at the fixture, then the wire needs to be replaced. This is normally done with the pool drained below the niche. If power gets all the way to the fixture, the fixture needs to be replaced. This can be done on the pool deck if there is enough wire to allow the fixture onto the deck. But if the wire is too short the pool may need to be drained.

    Checking wires can be done with the power off and a continuity tester, it can be done with a device that senses live wires nearby and either lights up or beeps, or you can measure power directly with a multimeter (though this last is more dangerous and requires proper understanding of safety procedures).
    19K gal, vinyl, 1/2 HP WhisperFlo pump, 200 sqft cartridge filter, AutoPilot Digital SWG, Dolphin Dynamic cleaning robot
    Creator of PoolMath and Pool Calculator. Other handy links: Support this site, TF Test Kits, Pool School

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    spishex's Avatar
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    Re: troubleshooting pool light

    Quote Originally Posted by JasonLion
    If there is power at the junction box, and is not power at the fixture, then the wire needs to be replaced. This is normally done with the pool drained below the niche. If power gets all the way to the fixture, the fixture needs to be replaced. This can be done on the pool deck if there is enough wire to allow the fixture onto the deck. But if the wire is too short the pool may need to be drained.
    Whether the problem is the fixture or the cord, both have to be replaced as one. Everything from the fixture to the junction box has to be one sealed piece, which is why lights are manufactured with cord attached and purchased with varying lengths (usually 10'-100'). Otherwise you'd be risking whatever junction you created leaking power into the pool.

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    Re: troubleshooting pool light

    Quote Originally Posted by spishex
    Was there water inside the housing when you removed it? Once a fixture has been flooded inside and out for a while the whole thing can get corroded beyond repair. Whether the issue is the housing itself, or the wire between the housing and the junction box, you'd have to replace the entire thing either way.

    You need a meter first off. From there, check the incoming power at the junction box, and then either test for continuity on the light line (a 250W, 120v bulb should be about 55 ohms I think?) or remove the light and check for power on the light terminals. If you're able to get it working you'll also need to replace the lens gasket if you haven't done so already.

    If you end up having to replace the entire fixture as simicrintz suggested you'll need to know the cord length required to get from the pool to the junction box. This is the easiest solution and ensures that you've got a good, safe housing that won't require attention again anytime soon.
    There was no water inside the housing, it was bone dry. And to me, the bulb itself looked fine too, although I replaced it anyway just to see. I did buy a new gasket too.

    Thanks for the information on what to test using the meter. I plan to pick one up on my way home from work and do exactly as you suggest.
    ~12k gallon in-ground pool, PebbleTec surface, sand filter, The Pool Cleaner (2WD)

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    Re: troubleshooting pool light

    Quote Originally Posted by JasonLion
    The next step, which can be done with water in the pool, is to test continuity of the wire. There is presumably power at the circuit breaker panel, so the question is how far does it get from there. The most likely problems are between the junction box and the fixture, but there could also be a problem between the breaker panel and the junction box.

    If there is power at the junction box, and is not power at the fixture, then the wire needs to be replaced. This is normally done with the pool drained below the niche. If power gets all the way to the fixture, the fixture needs to be replaced. This can be done on the pool deck if there is enough wire to allow the fixture onto the deck. But if the wire is too short the pool may need to be drained.

    Checking wires can be done with the power off and a continuity tester, it can be done with a device that senses live wires nearby and either lights up or beeps, or you can measure power directly with a multimeter (though this last is more dangerous and requires proper understanding of safety procedures).
    Excellent. I will pick up a meter on my way home and do these tests. I am fairly certain that there is power at the junction box and switch, but I will verify that with the meter.

    Thanks again.
    ~12k gallon in-ground pool, PebbleTec surface, sand filter, The Pool Cleaner (2WD)

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    Re: troubleshooting pool light

    Quote Originally Posted by spishex
    Whether the problem is the fixture or the cord, both have to be replaced as one. Everything from the fixture to the junction box has to be one sealed piece, which is why lights are manufactured with cord attached and purchased with varying lengths (usually 10'-100'). Otherwise you'd be risking whatever junction you created leaking power into the pool.
    This reflects what I see when I pull out the fixture: the cord and fixture appear to be permanently "sealed" together. As a matter of fact, there doesn't appear to be much to it (the fixture and cord) really, which is what has had me wondering what the problem could be between the junction box and fixture. There just does not appear to be much that could go wrong really.

    If I have power at the junction box, yet find that there is no continuity between there and the light, I think at that point my best bet is to just call someone out to look at it and either fix/replace what I have, or upgrade to a fancy new LED light. Either way that is beyond my comfort level with this work.

    I really just want to be as informed as possible before I call someone out to my house.

    I will post back with what I find out, thanks to everyone!
    ~12k gallon in-ground pool, PebbleTec surface, sand filter, The Pool Cleaner (2WD)

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    Re: troubleshooting pool light

    OK, problem solved, my light is working again.

    I picked up a multimeter on the way home from work today and ran a continuity test across the fixture\bulb wiring and it was fine. Then I tested for voltage at the junction box and found I had none. This led me to the GFCI outlet below my junction box, which turned out to be the issue. A quick replacement of that and problem solved.

    Thanks to everyone for their assistance. Now I just need to put my new gasket in my fixture, test it for leaks, and once that is good, refill my pool and get on the BBB program with hopefully a fresh start (read: lower CYA than before)!

    Thanks again, I will post my numbers once my pool fills and I get it tested.
    ~12k gallon in-ground pool, PebbleTec surface, sand filter, The Pool Cleaner (2WD)

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    spishex's Avatar
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    Re: troubleshooting pool light



    Meters are worth their weight in gold.

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    Mod Squad JohnT's Avatar
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    Re: troubleshooting pool light

    Quote Originally Posted by pebble.pool.fool
    This led me to the GFCI outlet below my junction box, which turned out to be the issue. A quick replacement of that and problem solved.
    John's #1 rule of household electricity: Always suspect the GFCI, even if it doesn't seem to be part of the circuit.
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