If there's one thing that drives me crazy, it's having a set of lights stop working in the middle of my holiday decorating.
I've been decorating for the holidays for a long time now, and there are certain things that I've learned over years of experience (and not always the easy way haha). This should at least help you fix a few of those pesky lights before you toss em!
Step 1: Check to see if any of the bulbs are either missing, broken, or visually burnt out. If the bulb is burnt out, it will have a blackish colored ring around it, or the fuse in the bulb will be disconnected. Replace broken, or missing bulbs.
Step 2: Check the wiring. Make sure that wiring hasn't been damaged or compromised. If wiring is visible, there may be a good chance its been damaged.
Step 3: Replace the fuse. Look on the plug and you will notice there's a small compartment that can be opened to replace the fuse. It's best to use a screwdriver or other tool to open it.
If all of these steps don't fix your problem, it may be time for a new set of Christmas lights. Luckily they're fairly inexpensive, but maybe that's why we're having these issues to begin with! Good Luck :)