You may find that the bulb has a black or silver looking stain on the inside.
How to check christmas lights that don t work.
For families intending to use the christmas lights year after year troubleshooting these lights may be necessary.
Check the entire strand of lights for a missing damaged or abnormal looking bulb according to the christmas light company website.
If this is your problem carefully replace the bulb after first unplugging the string of lights.
Https amzn to 2oebr6z amazon associate link this video shows how incandescent mini lights work and how to diagnose problems tha.
I also tried a light keeper pro to get a string of lights working.
Buy the light keeper pro.
The christmas light tester will indicate which bulbs are bad and need to be replaced.
Sometimes that makes more sense and can work even faster but it can t always repai.
In regions on 230v mains rather than 110v the shunt usually does its job.
Each holiday season i unpack untangle and plug in the previous year s mini lights only to discover that they don t work.
Basic mini christmas lights are typically three wire strands.
Second test the christmas light bulbs with an inexpensive tester available where holiday lights are sold and online usually changing a problem bulb or tightening it will fix the entire strand.
A failsafe called a shunt in each bulb is supposed to prevent this by closing the gap across the burnt out bulb but these often don t work properly.
Christmas lights are connected in series meaning the whole string will go dark when one bulb fails.