Pool light not working: GFCI, sync and bulb checks

Common symptoms

• You flip the switch and the pool stays dark.
• The GFCI outlet or breaker trips the moment the light comes on.
• The light flickers, then goes out.
• You see fog, water drops or a brown, burned look inside the lens.
• Color lights show different colors, or one light is out of step with the others.
• Every low-voltage light around the pool is out at once.

Quick checks before anything else

• The breaker for the pool light is on.
• The GFCI has not tripped. Reset it once.
• The wall switch, timer, light controller or automation app is set to on.
• There was no recent power outage or brownout (both can knock color lights out of sync).
• Other lights on the same switch or transformer work.
• From the deck, the lens looks clear, with no fog or water inside.

What causes a pool light to stop working?

• Tripped GFCI or breaker The light is dead, or the GFCI trips when you switch it on.
• Switch, timer or controller The light works by hand but not on schedule, or the controller is off.
• Color lights out of sync Lights turn on but show different colors or shows.
• Water inside the fixture Fog or water behind the lens from a worn lens gasket. Often trips the GFCI.
• Burned-out bulb or failed LED Power reaches the light, but it stays dark.
• Transformer or wiring All low-voltage lights out at once, or a loose connection at the junction box.

Step-by-step: how to fix a pool light that is not working

When a pool light is not working, we start at the breaker and work toward the light. Most fixes in the first half are free. The second half covers what a pro does, so you know what you are paying for.

1. Check the breaker and the controls. Make sure the light’s breaker is on and the switch, timer or controller is set to on. Hayward’s light guide says to verify the controller is active and the breaker or GFCI has not tripped. If the light works from the switch but not on a schedule, the timer or automation settings are the problem, not the light.
2. Reset the GFCI once. A GFCI (ground-fault circuit interrupter) cuts power fast when current leaks to ground. The CPSC says the National Electrical Code has required GFCI protection for underwater pool lights since 1968. Pentair’s first fix for a light that will not turn on is to check the ground fault and reset it. If it holds and the light works, you are done. If it trips again, stop here and call an electrician.
3. Check the transformer on low-voltage lights. A 12 or 14 volt light gets its power from a transformer (a box that steps 120 volts down). If every low-voltage light around the pool is out at once, the transformer or its circuit is the likely cause. Hayward notes that an overloaded transformer can also throw color lights out of sync. Opening a transformer or junction box is work for an electrician.
4. Look at the lens. From the deck, with a flashlight, look for fog, water drops, rust or a burned look behind the lens. Any of these means water got past the lens gasket. Keep the light off. The fixture has to come out, and Pentair says to always fit a new lens gasket when it is reassembled. Cloudy pool water can also make a working light look dim; see cloudy pool water.
5. Resync color lights. Color lights that are out of step can look broken. Hayward says power outages, brownouts, repeated toggling, voltage drop and an overloaded transformer can all cause this. For Hayward ColorLogic lights on a switch: turn the light on and wait at least 60 seconds, turn it off for 11 to 13 seconds, then back on. Check that all lights match, then turn them off for at least 2 minutes. Hayward says the off time must be timed for this to work.
6. Check the color mode. Hayward ColorLogic lights can run in four modes, and Hayward says all lights must be in the same mode to stay in sync. Its guide has a timed sequence (three off cycles of 11 to 13 seconds) that makes the light blink a color pair showing its mode. If one light differs, use Hayward’s change-mode sequence, then leave it off 2 minutes to lock it in. For Pentair IntelliBrite, each show or fixed color is a set number of off and on flicks of the switch; for example, six flicks select California Sunset.
7. Know what replacing the light involves. Pentair calls for at least 4 feet of spare cord coiled in the niche (the can in the pool wall), so the light can be lifted onto the deck without draining. With the breaker off, the pilot screw at the top of the face ring comes out and the light lifts free. Pentair warns to keep that screw, because it mounts and grounds the fixture. Pentair also says its underwater lights must be installed by a licensed or certified electrician or a qualified pool serviceman.
8. Replace the bulb or LED with the same type. If power reaches an incandescent light and it stays dark, the lamp is the next suspect. Pentair’s Amerlite manual says to use the same type and wattage of lamp and a new lens gasket every time. On an LED light like IntelliBrite, Pentair says to replace the LED assembly with the same type and wattage and use a new lens gasket. Fill the pool so the light is fully under water before running it more than 10 seconds.
9. Have the wiring checked. If power reaches the switch but not the light, Pentair’s guide says to check the wiring connection at the junction box by the pool and at the switch. Pentair says never to splice wires under water or behind the niche. A damaged cord gets replaced as one piece through the conduit, which is an electrician’s job.

Pentair vs Hayward vs incandescent lights

The big difference for troubleshooting is how color lights are told what to do. Switched lights read the timing of power going off and on, so a flicker in the power or a rushed switch can scramble them. Network lights take commands from the controller, so you resync them from the controller or app. If your robot cleaner also stopped at the same time, see robotic pool cleaner not working; its power supply has its own GFI. The pool lights and cleaners hub lists the specs for each light.

When to call a pool or spa pro

• The GFCI trips again after one reset. Hot tubs trip for similar reasons; see hot tub GFCI keeps tripping.
• There is water, fog or rust inside the lens.
• All low-voltage lights are out and the breaker is on.
• The cord is too short to lift the light onto the deck, or the cord is damaged.
• The light is loose in the wall, or the pilot screw is missing.
• You smell burning at the switch, transformer or junction box.

Common questions