If you replace your UV lamp and the new lamp doesn’t come on, here are some things to consider:
Give the lamp time. UV lamps are like fluorescent bulbs. Sometimes there will be a delay of several seconds, even up to a minute, before the lamp comes on. And there may be some flickering at the beginning.
The red safety switch button on the bottom of the control module (UV20, UVB, and UVBB units) must be depressed for the lamp to burn. Check that.
Be sure that the problem isn’t the fuse. If the fuse is bad, nothing will work.
Be sure that the problem isn’t the LED. If the LED on the face of the power supply does not come on, the unit can still work and the lamp can burn. Be sure that the problem isn’t simply that the LED bulb has burned out. Test this by pushing the red safety switch with the lamp installed, avoiding direct eye exposure to lamp.
If the lamp is bad, the LED will not come on even if the LED is functional.
If the unit was working normally before you replaced the lamp, the best test you can do is put the old bulb back into the unit. If the unit works normally with the old bulb, with the lamp burning and the LED burning, it is almost certain that the lamp itself is the problem. If neither lamp lights, it's likely that the power supply needs to be replaced.
(whole house & well units)