Yes, LED christmas light strands are often two independent circuits.

The LEDs are connected in series, so if one is disconnected or somehow failed open circuit, that circuit will go out. Of course the same will happen if there is a break somewhere in the wire.

You could check with a voltmeter to see if you are getting 120vAC out of the socket on the tail end, which if zero would mean a wiring break.

But I think chances are you have one failed LED.

Further testing would mean cutting into the strand.

The small catch in you plug is where the fuses are. You should find two of them in there. I am not sure where you are located but I get my replacement fuses at Walmart and its a lot cheaper and less time consuming to start with that. Give it a try and thanks for the Christmas Spirit....Good luck.

UPDATE

just added an image due to another question about this....

Good Evening to All and may all your lights work. I encountered the age old problem of half the strand not working. I discovered it before I put it up on the eaves. This year I got an early start on my lightscape so I had time to troubleguess the offending strand. I inspected the wire for breaks. Then plugged it in to the wall socket. I removed one LED at a time starting at the plug end. After the sixth LED I was ready to quit. #7 proved to be the problem. The prongs of the LED were misaligned in the base so they couldn't make contact with the socket. I pushed the prongs into position, put the LED in the socket and "bam" the rest of the strand came to life. The whole task took 10 minutes. The best part is that I was able to live up to the expectation of my 7 year grandaugther who was observing the proccess. In her words, "Good job Granpa". I hope this answer is helpfull to someone. Happy Holidays from Phil in Kansas.

This business of flipping the plug, using oscilloscopes, or noting hz is all indicative of not understanding Diodes. LED's (Light Emitting Diodes) only work with the current flowing through them in one direction... direct current. Alternating Current (your house current) fluctuates or oscillates 60 times a second.. hence "60 hz". In order for your LEDs to wok on that circuit they need half of those oscillations to be eliminated. They also need the voltage to be greatly reduced.... from 110 down to about 5. LED's also cannot be tested like an incandescent string of lights using an ohmmeter because they have no filament. Testing a bring of LED's would require setting up your multimeter as an ammeter, breaking and testing the light string only (not the other two lines.

Because the string is made to work AS A WHOLE UNIT with AC power, the observation that flipping the plug should alert you that this function has been destroyed. The fuse was there to prevent further damage (fires). The fact that you can replace them should also bring with it the caution that you need to find out what caused the failure in the first place.

A shorted bulb in one of your strings most likely caused a failure in a diode that changes that 110v AC to DC . That event likely caused the fuse to blow. Replacing the fuse or flipping the plug does not address the root problem, and my bet is that you will have to toss the string and buy new.

While you are inspecting your defunct string, break into and have a look at an LED. See that the two electrodes inside are different sizes. The large one is the negative side, the small is the positive. There is space in between... no filament. The polarization of the two poles, and not current flow from one to the otheris what makes that space in between give off light. In fact, if the voltage is too high (AC or DC) that space will be violated and the LED will literally "pop its top". Depending on the element in that matrix, you get different colours. Red is the cheapest light to produce. Clear light is one of the most expensive.

Same problem, new solution. I tried new fuses and still the one end of each string would not light up. So I thought...Since one string has the plug end that won't light and the other has the receptical end that won't light, what if I cut the strings and put the two ends that do work together? Making sure that I connected the one wire that runs straight thru the entire string to the same on the other side and the other wire that goes into the bulbs together I now have a complete string of working lights. Forgive me but...I somehow feel like a genius right now :). And a special thank you goes out to my daddy, who passed away on Christmas Eve in 1981, for letting me tinker in the garage with him when I was a child. And to all a good nighttttttttttt!

half a string is better than no string, cutting the 'broken half' off makes sense - as long as the good half still works afterwards

merry x-mas

I have never seen light strings with fuses in the plugs will have to look again, but what we DO have is light strings with "Fusible Links". These strings may well have more than two light series in them, separated by a fusible link on each end of the series. Imagine a ladder where the legs of the ladder represent each side of a 110 volt circuit. The light strand(s) are the rungs with perhaps 20 lights per strand. At the intersection of the "legs" and "rungs" you have a fusible link. If a short or a break occurs in any of the light strands, one or both of the fusible links will blow, are sealed for life, and are not serviceable. That light strand will be out and the rest of the strands will remain lit. The fusible links are for safety, not for convenience.

Now for a bit more info. If you try to cut out the fusible links or even replace them with a more serviceable unit, you need to understand something about LED's as opposed to incandescent lights. LED's operate on Direct Current (DC) and will only light with that current running in one direction. They would blow up (literally) if applied to 110 volts AC when they are designed for more like 6 volts DC. So in every light base, or as part of the fusible link, there will be another diode whose job it is to create that DC low voltage. To remove that is to invite disaster.

If you have a string failure, best to cut your losses and go get yourself a new one.

This isn't the same thing as testing for bad lights and replacing them. This is quite different. Meantime, I'm gonna keep my eyes open for those one with replaceable fuses.....

I have the same problem. Half of LED string of lights come on -- the other half does not. Unplug and flip plug 180 and replug and the other half comes on -- and the half that did work now does not. There are no bad LEDs. Every one comes on at one time or the other.

If you get one half to light its not the fuse as one fuse is for both halves

I have the same problem and i tried to fix it, my Christmas lights are 120v and 60Hz AC. The problem is when i brought m lights out and plugged them in, for some reason the whole entire light string wasn't working. So i looked at the fuse and the fuse was OK, so then i looked for any bad light and i think i found it. I went to the market to buy a replacement and found out the old bulb was bad. But apparently when i plug it in the lights light up but only half way. So fro not working i got to work but it only works have way. what can i do to fix it. Please inform me by step by step on how i should fix my lights.

Thanks, but you see i can't replace the whole entire half string. And i do have a multi meter with the positive and negative leads but where do i check (place them) to find out if the circuit is flowing freely

Sounds like one of the strings is only passing dc instead of ac resulting in one half of the string being lit. reversing the plug would allow the dc to light up the other side of the string. Connecting directly to an outlet would allow ac and both halfs would light. Your problem appears to lie in a string of lights before the affected string.

Buzz

How do you open and check the fuses? Is it where the plug is, or the little cylindrical thing near the plug? Both look encased in plastic, with no opening...

hmm..same problem. These LED's contain NO fuses and the bulbs are not removable. Half a strand out, flip the plug 180 degrees and the other half is out. This set is in the middle of about 10 sets, and the lights before, and after work fine. screwy..

my particular LED's operate on AC (noticeable strobe/flicker in peripheral vision much like an old CRT tv)

I looked at the strand and actually pulled an LED out, and there is in fact, no diode. There is also no in-line box or anything indicative of additional in-line electronics. They also pass 120V AC to the next strand (and in my case, through 10 strands) because they power small incandescent mini light globes at the end.

A friend of mine just put up all his led strands and low and behold there are at least 3 or 4 sets out of 15 that are completely dead. They worked last year and were stored indoors, not abused or damaged.

this kind of LED christmas gifts 2011 light string? is it worth trying to replace the fuse? (of course, it would only make sense doing so if there wasn't some other more serious fault in the circuit

LED lightsets that are used outdoors are prone to water leakage and subsequent corrosion of the LED leads inside the sockets. Pull the LED's out of their respective sockets in the string. If the leads are rusty, the LED's will need to be replaced. Don't try to clean them if they are rusty. The sockets can be cleaned with a bit of WD-40 and a small screwdriver (please do this with the string unplugged). New LED's can be inserted into the holders. Pay attention to the orientation of the LED's in the sockets. There is usually an indicator on the LED holder that shows a "long" side and a "short" side. Place the new LED into the socket with the long wire on the long side, short wire on the short side. Bend the leads back slowly. They are steel and are not as flexible as brass or bronze leads that are common on the older mini-bulbs. Stop by the automotive dept. and buy a tube of dielectric grease. Squirt some of that grease into each socket before you place a new LED into the socket. That will prevent further corrosion. When you buy new LED strings pull each LED out and coat the contacts in each socket with the dielectric grease before you place the string into service. Replace the LED's back into the sockets, push the securing tab down and your new corrosion proofed lights should last a very long time time. Good luck!

Ok, so I am having the same problem. Half of strand works, other half is out. The next strand in the series works so I am assuming that it is not a break in the wire and must be a bulb. Would it be the first bulb in the series that is out or could it be any of them?

Last night I had the good ole plug them in and 2/3 of the lights do not come on AFTER testing them in the garage. I have found out a couple of useful things. The strands that I am talking about are the C9-100LED's. 1) These starnds are actually split up into 3 sections and a bulb going out will kill that section of the strand. On the 1st section I checked 8 lights before finding the bad one the second was 15 before I found the culprit.

2) the Christmas Light Tester/Repair Gun can test a LED bulb BUT the bad part is that the buld socket is too big to fit inside the opening that over rides the strand and make the rest of the bulbs work.

I hope this helps.

just "cut out" the ones that don't work (since the actual bulbs cannot be fixed). Then reconnect the lines together ( i use the plug that you crimp and then heat to melt the connector to the wire), then insulate with a lot of electrical tape and you voila...done. It will be shorter but it will work.

it was easy to replace the bulb every string comes with replacements.