Why is the UV light not turning on in my UltraKlean Pond Filter? April 18, 2026 02:38 Common causes:Timer not setNo power to unitLoose bulb connectionBulb expiredCheck that the 4-prong bulb base is fully seated and the system is powered Related articles Videos and Troubleshooting Why is my UV light not turning on? Why does my UltraKlean Pond Filter still have green water? UltraKlean Replacement Parts Why is my UV indicator light off?