On my house, I have 3 strands of C-9 Christmas lights strung together in series.

When I plug them in, they turn on and everything works fine for about 20-30 minutes. At that point, the fuse at the beginning of the first strand (connected to the power source) blows. I've replaced it twice already with the recommended fuse (125V, 5A), but the same thing happens.

I've used these same lights on my house for 3-4 years without any major problems. For some reason it seems like I did blow a few fuses when I first plugged them in last year, but I don't think I did anything to get them to a steady state other than just change the fuse a few times.

Any ideas of what might be wrong or how to test/fix it? Thanks in advance.

(Cross-posted in Home Improvement and The Nerdery.)

I believe those lights will say 2 strands maximum. I had the same issue last year and ended up having to run numerous extension cords all over to keep the lights from blowing fuses.

Good luck.

You can take the fuse out, and create a solid connection with a piece of wire to make it work. It is a complete fire hazard, so take your chances, but in a pinch it works.

I was hanging lights for some widows at my church this weekend and ran into a string of rigged fuse-less lights. One of the bulbs broke and shorted and it started shooting fire balls the size of softballs out of the socket and didn't stop until we unplugged it.

Try testing them one at a time the start adding the additional strands on a different outlet. If the same thing happens you might have a bad strand.

I'd just upgrade to LED's.

Had a friend that bought new LED's for the front of his house and hung his old lights on his kids tree house and it looks awesome and the kids love it.

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I believe those lights will say 2 strands maximum. I had the same issue last year and ended up having to run numerous extension cords all over to keep the lights from blowing fuses.

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That's correct. Each of those strings pulls about 2 amps, so plugging 3 in together pulls more than the 5 amp fuse can handle. You can put a bigger fuse in there, but I don't remember if they make any that will fit. You might see the cord heat up a little, but you shouldn't run too much of a risk having 3 together. I just wouldn't put anymore than 3 in a line.

Thanks for the responses.

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Each of those strings pulls about 2 amps, so plugging 3 in together pulls more than the 5 amp fuse can handle.

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I confirmed that the manufacturer recommends stringing no more than 2 together, so this makes sense, but what might have allowed the same setup to not burn a 5A fuse in previous years?

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it started shooting fire balls the size of softballs out of the socket

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sweet!

While we're on the topic...

We have a pre-lit artificial Christmas tree that had a whole section of lights burnt out. I noticed that each bulb is darkened inside the glass, so it doesn't seem like your typical case of just one being out. Would a fuse going out cause this or what? Should I just replace each one of the bulbs?

Each C9 bulb is 7 watts. Assuming each of your strands is 25 bulbs, that makes for 1.46A/strand. 3 strands would be 4.38A.

I've seen it where 4 strands all plugged together works and I've seen cases where 3 stands together blows the fuse. Each situation can be funny. This still doesn't really explain why you've been able to do it in yours past without your fuse blowing......

Most C9 strands use 18 or 20 gauge wire. If yours is 20gauge which is not meant to handle more than a few amps at a time.

www.lightsofnazareth.com

I bet the discrepancies are due to being made in China

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We have a pre-lit artificial Christmas tree that had a whole section of lights burnt out. I noticed that each bulb is darkened inside the glass, so it doesn't seem like your typical case of just one being out. Would a fuse going out cause this or what? Should I just replace each one of the bulbs?

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When a bulb burns out, normally a built-in shunt will bypass the blown bulb - I say 'normally' because sometimes it doesn't work and you still end up with an open circuit. So - unless you have a LightKeeper Pro or some type of string checker, I'm afraid you'll need to go through the bulbs one-by-one...

www.lightsofnazareth.com

[This message has been edited by txag2008 (edited 12/8/2010 3:41p).]

Wrap the fuses in foil. You should be ok.

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what might have allowed the same setup to not burn a 5A fuse in previous years?

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Dirt/crud. Unscrew each bulb and rescrew it in. Might continue to work...

Hi. I had exactly the same problem as karmapolice above. I had 4 strings together, and reduced it to two. Then I remove each bulb (they were over 10 years old) and polished the threads and contact point with fine steel wool. Then I applied a small amount of dialectric grease to the threads and contacts. Added a new fuse, and Problem solved! The bases of many of the bulbs had notable corrosion, much like the terminals on a car battery acquire. I think because they are outside in all kinds of wet weather the minerals and pollutants in rain/snow must contribute to the corrosion. This can be a time consuming task if you have a lot of bulbs to clean; I only had 48 to 50 bulbs. But it was a time of year when new bulbs were scarce, and it saved me from buying more strings of lights. Good Luck!

Also, I noticed that the strings of lights were labeled as to the limit of bulbs to link together. For my brand it boiled down to no more than 60 bulbs, which converted to two strings (about 50 bulbs). This may require some creative use of extension cords with multiple receptacles, but it saves a lot of aggravation in the long run.
Merry Christmas!

Highly recommend upgrading to LED. Makes this a moot point. You can string together like 20-25 strands.

holy thread bump

Asked Google: C9 fuse popping. This thread was the first listing.

TexAgs knowing stuff.

rononeill said:

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Asked Google: C9 fuse popping. This thread was the first listing.

TexAgs knowing stuff.

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It's Santa telling you to slow your roll on the Christmas lights

A popular topic this week I see. I'm here for the same reason.

I've had three sets of 25 count C9 incandescent ground lights strung together for probably eight years now. Never blown a 5 amp fuse before. Been electrical taped together all this time so they always stay connected in the same order. This year I go install them and they immediately blow the fuse in the first set. After some troubleshooting I get out an inline power meter and discover that the first two sets are drawing 1.5 amps each just like they should. However, connecting the third set by itself to an extension cord with the power meter in the loop shows it initially pulling 7.8 amps the first second, 5.6 amps the next second, and then stays right at 5.1 amps for about 30 seconds or so and then it starts slowly dropping down. Lowest it gets to with the lights warmed up is 2.1 amps.

Definitely something wrong with that third set. LED time for me.

txag2008 said:

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We have a pre-lit artificial Christmas tree that had a whole section of lights burnt out. I noticed that each bulb is darkened inside the glass, so it doesn't seem like your typical case of just one being out. Would a fuse going out cause this or what? Should I just replace each one of the bulbs?

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When a bulb burns out, normally a built-in shunt will bypass the blown bulb - I say 'normally' because sometimes it doesn't work and you still end up with an open circuit. So - unless you have a LightKeeper Pro or some type of string checker, I'm afraid you'll need to go through the bulbs one-by-one...

www.lightsofnazareth.com

[This message has been edited by txag2008 (edited 12/8/2010 3:41p).]

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In this case, the lights on either half or the entirety of the string have burned out. With typical mini-lights, as individual bulbs burn out, this causes added load to be transferred to the remaining bulbs located along that segment of the string. The remaining bulbs will burn much hotter and brighter, drastically shortening their lifespan. The mirrored area you are seeing inside the glass is caused by the excess heat at the remaining bulbs prior to burning out. Generally, the most straightforward route of repair is ripping the entire string off the tree and replacing them, as it can be extremely difficult to find replacement bulbs in the quantity you would need to replace the existing string(s).

If you do this, I would recommend biting the billet and replacing the lights on the entire tree, as the other strings likely have burnt out bulbs which will lead to the same problem in other areas of the tree, since they will have all had the same service time. If you do decide to this and are using incandescent lights, I would recommend buying a bunch of boxes of the 50 and 100 count GE lights sold at Lowes, as these are generally the most reliable incandescent lights available at big box stores (they are often located on an end cap, FYI). The reason for buying both 50 and 100 count strings is so that you can terminate the light runs as needed to still allow each tree section to separate. Lastly, if you are working with incandescent lights, be mindful of the max number of strings when can be connected end to end; you may need to run an extension cord up the tree to connect the lights into.

The process is a pain (I have done this with two trees this year), but should hold you over for 2-3 years at least. Plus, replacing the lights again down the road will be much easier, as the strings will be of a typical length and type available at retail.

Lastly, if anyone is looking for a source for high quality Christmas lights and accessories, check out Christmas Lights Etc. out of Alpharetta, GA. They run fairly frequent sales on their website, particularly in the off season.