Troubleshooting Prelit Christmas Trees

Troubleshooting common issues with prelit artificial Christmas trees can often be completed within a matter of minutes. Most troubleshooting in trees centers around light strings that have gone dark, or the initial assembly of the new tree. Methods in troubleshooting include testing the light strings in an effort to find the faulty bulb, or simply replacing the existing light strings with working sets. Below you will find the most common problems and solutions associated with light strings on prelit Christmas trees.

How to Replace Christmas Light Fuses

4 Basic Steps for Troubleshooting Prelit Trees

Step 1

If the tree has multiple light plugs stacked together, the most common reason for a section not turning on or flickering is often as simple as one of these plugs coming loose. Check that all plugs are secure. If your tree is a power pole or one plug design, check each section where the poles meet to ensure that there is nothing obstructing the connection and that they are seated properly.

Troubleshooting Prelit Christmas Trees -Check that plugs are secure

Secure All Plugs

Step 2

Check the plug fuses. Slide open the door of the plug and replace any fuses that look burnt out. Then plug the strand into an extension cord to see if this fixes the problem. Need help? Watch this video on replacing fuses!

Troubleshooting Prelit Christmas Trees -Inspect Fuses

Inspect Plug Fuses

Step 3

If the fuses all look fine or replacing them does not fix the problem, there may be a problem with a bulb or the wiring itself. Replace any damaged bulbs with spare ones. If the issue is with the wire itself, remove the entire string and replace with a new strand of lights. In older trees all of the light wires may need to be removed at some point (snipping them with wire cutters makes the job faster), you can then restring the tree with lights, which will allow you to keep your cherished tree for even longer!

Step 4

If no bulbs are damaged, test each bulb with a bulb tester, these can be found online and in most big box hardware stores.

Replace Bulbs as Needed

Troubleshooting Incandescent Prelit Christmas Trees

Troubleshooting and fixing an incandescent prelit Christmas tree can be easier with the use of a mini light tester. If using a mini light tester, our resource page regarding Testing for Faulty Bulbs, will prove useful.

"One Light Goes Out The Rest Stay Lit"

Understanding the technology behind an incandescent bulb and a light string is helpful when trying to determine the cause of a bulb that won't light. Each bulb is lit through a filament, which is contained within the bulb's glass case. Most modern light strings feature "One light goes out, the rest stay lit" technology which is achieved through an internal shunt within each bulb.

The internal shunt does not have any effect unless a bulb's filament burns out, at which point the shunt wire activates to keep the current going. As long as current is flowing through each bulb the strand will remain lit. A broken bulb will not affect the rest of the strand, unless the shunt is broken in the process. If the shunt is broken when a bulb breaks, or if it is dislodged due to a loose bulb, the flow of electricity will stop.

Another reason for light failure is connectivity lost at the base of the socket. Two thin wires stick out at the bottom of each mini light bulb, which make contact with the metal connectors for current to the bulbs and shunts. If one of the wires is misaligned, or if a bulb is pulled out from its socket, the current is broken and the light strand will go out. To verify the wires are in place, remove the socket and make sure a wire is folded up to the left and right of the socket base. These wires are actually part of the glass light bulb itself, which are guided through two small openings at the bottom of each socket and then folded upwards. If needed, simply realign the wires on each side of the bulb, or if one of the wires is missing, replace the bulb.

Thin Wire on Either Side of an Incandescent Christmas Light Bulb

Common Problems with Wiring & Bulbs

If lights go on and off as the tree and branches are moved around, this is not always an indication that there is a short in the wire. Most likely a bulb is loose, and the connection is getting lost as the bulb moves in its socket. This often occurs through rough handling or improper storage of a tree. Look to find the loose bulb, check the wires to ensure they are properly aligned, and secure the bulb tightly within the socket. This should fix the issue.

If a short has occurred, the light string is usually not repairable. A short is caused when the wire's insulation breaks down, allowing charge to flow in an unintended path. Common causes include cutting or damaging the wire itself, or overloading the circuit by plugging too many devices into an outlet or adding additional strings of lights without calculating wattage and amps. Our light strings are fused for protection, so overloading the circuit will cause the fuse to break and the light string will go out, but will not be damaged. Look for broken fuses in the male end of the light string, and replace using one of the extra light fuses that are included with the tree. A good fuse will have clear glass, while a broken fuse will cause the glass become tinted. When checking for broken fuses and replacing fuses, make sure the light string is not plugged into the outlet.

Troubleshooting can be easier with the use of a mini light tester. If using a mini light tester, our resource page regarding Testing for Faulty Bulbs, will prove useful.

"One Light Goes Out, Rest Stay Lit" is a technology that uses an internal shunt within the bulb to continue the flow of electricity throughout a light string, even if a bulb has burned out. It is important to understand that if the shunt is broken when a bulb breaks, or if it is dislodged due to a loose bulb, the flow of electricity will stop.

Additionally, each mini light has two small copper wires that come out of the base of the bulb, and fold upwards on each side. When the socket is in place and the bulb is secure, this allows for the current to continue to flow. Sometimes the copper wire may be broken or out of position, and replacing the bulb or moving the copper wires into place should remedy the problem.

Christmas Light Bulb With Internal Wires

Troubleshooting LED Trees

LED light strings feature one piece construction, which can make troubleshooting limited. Mini light testers do not work on LED trees. If an LED tree is not lighting, check to make sure all wires are plugged in and fuses are securely seated. An LED light tester can also be used to identify which bulb or socket is not properly functioning.

Many times the main plug that goes to the outlet is not in the lowest section of the tree, which can seem confusing. Larger trees often have 2 or 3 plugs that go into the wall, so look for these if the tree does not light completely. Each of these plugs will also have a fuse, so check to make sure they do not need to be replaced if a section of the tree is not lighting.

LED Christmas Tree Lights

Tips for Prelit Christmas Tree Assembly & Storage

Keep in mind that trees do not arrive as pictured. Each tree has its own unique tip shape, which is achieved through a process we call "fluffing". It is best to start by shaping the lowest section of the tree before adding the next section of the tree. This allows each inner tip to be lifted up and out, and many lower branches are expandable, meaning the branch itself can be lifted up or moved to the side, and then the branch tips can also be lifted. Tree tips can be arched downwards, or left to shoot straight out. Plug in lights prior to fluffing each section. For step by step instructions on assembling your tree, visit our Christmas tree setup guide.

Christmas Tree Storage Tips

Are you a tree wrestler? If you spend way too much time trying to shove your fluffed Christmas tree back into the original box that has been taped shut too many times, only to have parts of it busting out of the sides, then the answer is yes! When you take the time to store your tree properly you'll have a beautiful, full tree for longer and you'll get to skip the headache that comes with having to unpack your smashed up tree the following year. The very best option for storing a tree is to use a proper bag for your tree size. Tree storage bags will keep the branches from getting bent and deformed while also protecting the delicate lights, wires, and connectors on your tree.