Troubleshooting Tree Lighting Problems

Christmas is coming, the lights have been strung on the tree and the front of the house...maybe even throughout the yard. Then, seemingly for no reason, they flicker and appear to short out, or worse yet, the whole thing goes dark. What do you do?

Here we illustrate situations which you have undoubtedly faced in Christmases past. Perhaps your solution was to toss out the "bad" strands and buy new lights; however, you could fix these problems quickly and easily. With this guide in hand, you'll save time and money by avoiding the need to replace "broken" light strands.

CHRISTMAS LIGHT CRISIS NUMBER 1: A single strand of lights doesn't work.

Possible causes:

Remember: Most of these repair steps require that you have the strand plugged in to locate the problem. Unplug once problem has been located.

CHRISTMAS LIGHT CRISIS NUMBER 2: A single strand of lights doesn't work, but it has other strands plugged into it that are working, or half a strand works.

Possible causes:

CHRISTMAS LIGHT CRISIS NUMBER 3: A strand of lights flickers on and off when moved or touched.

Possible causes:

CHRISTMAS LIGHT CRISIS NUMBER 4: A whole strand (or half a strand) starts to blink when it should not be blinking.

Possible causes:

Remember: Most of these repair steps require that you have the strand plugged in to locate the problem. Unplug once problem has been located.

CHRISTMAS LIGHT CRISIS NUMBER 5: The whole strand works ... except for one single bulb.

Possible cause: This one is pretty simple. Chances are, the bulb is either burned out or broken. See Cure No. 8

CHRISTMAS LIGHT CRISIS NUMBER 6: A replacement bulb is too big or too small.

This problem can be avoided by using the replacement bulbs that come with a specific strand of lights. If you find, however, that you have a variety of bulbs, the problem can be easily resolved. First, try to find a proper replacement bulb, which should have a snug fit (not too loose or too tight). If you don't have the right sized replacement bulb, see Cure No. 9.

CHRISTMAS LIGHT CRISIS NUMBER 7: One bulb is brighter or dimmer than the rest of the bulbs on a single strand. See Cure No. 10.

CHRISTMAS LIGHT CRISIS NUMBER 8 : Your Christmas lights come on at odd hours.

Possible cause: Your timer is not set properly. See Cure No. 11.

CHRISTMAS LIGHT CRISIS NUMBER 9: No strand works when plugged into a certain wall outlet ... or, all the lights were working, and now they don't.

Possible cause: A switch, circuit, or breaker issue. See Cure No. 12.

CHRISTMAS LIGHT CRISIS NUMBER 10: Your GFI circuit trips when it is reset, or for no apparent reason.

Possible causes: Blame it on the weather...or perhaps the lawn sprinklers. Either way, chances are that your outdoor light strands are saturated with water. See Cure No. 13.


Note: Do not throw away the bad or broken bulb you are about to change until your problem is solved. Be sure that the replacement bulb is not a blinker bulb, and that it is designed for your brand of lights (mixing different brands can cause bright or dim lights in the strand, or the plastic bases may not fit properly).


Two types of fused plugs are used:

Most replaceable fused plugs have a sliding door over a small compartment in the plug. Simply open the door and replace the bad fuse with a new one. The importance of this difference will be obvious to you when the lights are strung on the tree or house and one strand blows a fuse. If the strand has a replaceable plug, you have an easy solution to getting the strand glowing again. However, you put up a strand with a built-in fuse, you will have to take down the entire strand and replace it.

Troubleshooting and Replacing Safety Fuses

First, check to see if a test set will work if it is plugged into the socket of the strand which you think has a bad fuse. If the test set doesn't work, replace the fuse. If it does, go back to the Christmas Light Crisis list to check for another possible cause. If the fuse blows again, look for punctured or exposed wires (this is a rare problem, but if you find exposed wires, either discard the strand or have it repaired by someone familiar with electrical work).

Check to see that fuses are not touching inside the plug. Be sure the number of strands plugged together does not exceed the manufacturer's recommendations. If so, run an extension cord to the extra strands and plug them into it.


Cure No. 1: A Bad Plug Connection

Step 1: Find the plug end of the non-working strand.

Step 2: Pull the plug out, then put it directly back into the wall outlet. Try this once or twice. If the lights come on, your problem is solved!

Cure No. 2: A Bad Fuse in the Plug

Check to see if a test set works when you plug it into the socket of the strand which is not working. If the test set doesn't work, replace the fuse on the non-working strand.

Cure No. 3: Broken, Missing or Abnormal Bulb

Check strands for broken, missing or abnormal-looking bulbs (they may have a black or mirror-like stain on the inside of the glass casing). Replace with care, as broken bulbs can shock you.

Cure No. 4: Loose Bulbs

Use your fingertip (or a pen or pencil) to "flick" each bulb hard two or three times. Watch to see if the individual bulb or the entire strand flickers or flashes on. If this happens, you probably have a loose bulb. Carefully remove the bulb and check to assure that the center wire is centered on the base. If the center wire is damaged, replace the bulb.

Cure No. 5: Damaged Bulb

Take a pre-tested replacement bulb (the "good bulb"), remove the first bulb in the bad part of the strand and replace it with the good bulb. Chances are, this didn't work on the first bulb. However, continue replacing each bulb with the previous socket's bulb. (Remember, every socket needs to have a bulb in order to attain a working strand.) You can also purchase a Light Tester which can help you find the damaged bulb.

Cure No. 6: A Shifted Wire in the Light Socket

You may have to repeat this cure many times. The tricky part is that sometimes we think we have found the shifted wire when actually we have found the bulb next to the one with the shifted wire (in moving the good bulb, the bad bulb next to it causes the lights to flicker, making us think that the good bulb is the bad bulb). Patience and perseverance pays off here. If you're successful, there will be no waiting in the checkout lines at the store!

Cure No. 7: A Blinker Bulb in a Non-Blinking Strand

If no bulbs are broken, you will have to look for the "blinker blub" in the strand (which is clear except for a red-colored top, and some will have different-colored plastic bases). Check the first and last lights first. If they aren't blinker bulbs, check the rest of the lights. When you find the blinker, replace it with a standard replacement bulb.

Cure No. 8: The Bad Bulb

You'll need to remove it and put in a replacement bulb. Check to be sure that the new bulb is not too bright, too dim, too big or too small for the socket. We suggest that you replace all non-working bulbs because doing so will increase the life of the other bulbs on the strand.

Cure No. 9: Swapping the Plastic Base of the Bulb

Cure No. 10: Bulbs Brighter or Dimmer

Another piece of cake. Try a replacement bulb for this particular brand of lights.

Cure No. 11: The Timer

A timer on your Christmas lights can be a safe and simple means of turning your lights on and off without your having to plug in or unplug strands. But if your lights turn on or off unexpectedly, check the timer and reset the clock. You might also check to see if you have plugged the timer into an outlet that is controlled by a light switch.

Cure No. 12: Switches, Circuits and Breakers

Note: If your house is newer or remodeled, you may have GFI circuits that must be reset when tripped. (See Christmas Light Crisis Number 10). Most GFI circuits can be reset simply by pressing the RESET button. In some homes you may have to reset it on your main fuse box. If your circuit has tripped a breaker in your main circuit box, one of the breaker switches will be out of line from the rest. Flip the switch all the way OFF to reset the breaker, then flip the switch back to the ON position. If GFI switches are designated in your fuse box, reset them. (It is not normal for any circuit to switch off. If the cause of the tripped circuit is not immediately obvious in the above situations, contact your local electrical power company for other possible causes.)

Cure No. 13: Try each of these steps until the problem is solved: