Christmas Light Set & Fuse Tester, retail $6.99 *
Manufactured by (Unknown) for Radio Shack (
Last updated 09-12-10

The Christmas Light Set & Fuse Tester is a handy-dandy device designed to test Christmas light sets & bulbs plus the little fuses found in the plugs of most Christmas light sets.

It can test bulbs two ways.
1: Noncontact testing, where the defective light string is plugged in and you can find the bad bulb that way.


2: Tests bulbs the "old fashioned" way -- where the bulb is pressed into a "socket" on the tester, and a red LED on the tester lights if the bulb is good.

It can also be used to check those small fuses found in the plugs of most light sets -- when the fuse is pressed into a pair of contacts on the tester, a red LED on the tester lights if the fuse is good.

* This product appears to have been discontinued; I was not able to find it on the Radio Shack website.

 Size of product w/hand to show scale SIZE

To use the Christmas Light Set & Fuse Tester to find the bad bulb in a set of Christmas lights that won't fire up, plug the set in first. Then, press & hold down the yellow button on the tester, and wave it over each bulb. Start at the end of the set farthest from the plug first -- if the red LED lights up now, then unplug the set, turn the plug 180°, plug it back in, and try again. With a modicum of luck, the LED on the tester will remain dark now.

When the red LED on the tester lights, go back one (1) bulb, and change that one.

To test fuses, remove the suspect fuses from the plug of the light set, and press them (one at a time) into the pair of metal contacts labelled "FUSE" on the tester. Be certain that the metal end caps of the fuse touch the metal contacts on the tester. If the red LED on the tester comes on -- even if it just flickers a bit, that fuse is good.

This tester feeds from a pair of AG-13 button cells.

To change them, look on the back end of the tester for a large yellow cap with a pocket clip built into it. You'll see a small black tit near the center of the upper surface of this yellow piece. Using a medium screwdriver, press this tit in, and slide the yellow cap toward the back of the tester until it comes off.

Gently place it on the floor, and use your foot to push it under the Christmas tree that you're always forgetting to water so that the hungry, hungry darkling beetle grubs (larvae) will think it's something yummy for their insect tummies, drag it into the mouse hole in the wall, find it unpalatable, and then become angry at it and proceed to uranate on it...O WAIT!!! YOU'LL NEED THAT!!! So just set it aside instead.

Remove the two used AG-13 button cells from the battery holder, and dispose of or recycle them as you see fit.

Insert two new AG-13 button cells into the battery holder, stacking them atop one another and then oriening them so that their button-ends (-) negatives face down (as you're holding the unit so that the button & LED are on the top).

Slide that yellow cap back on, orienting it so that the pocket clip goes toward the upper surface of the unit (where the button & LED are). Push straight in on it until it snaps into place.

Aren't you glad that you didn''t push that end cap under the dead, dead Christmas tree with all of those darkling beetle larvae with full bladders now?

This is a Christmas light tester, not a flashlight designed to be carried around constantly, thrashed, bashed, trashed, and abused. So I won't try to drown it in the toliet tank, bash it against a steel rod or against the concrete floor of a front porch in effort to try and expose the bare Metalmarineangemon - er - the bare Metalkumamon - um that's not it either...the bare a sec here...THE BARE METAL (guess I've been watching too much Digimon again! - now I'm just making {vulgar term for feces} up!!!), let my mother's big dog's ghost or my sister's kitty cats spring a leak (uranate) on it, hose it down with a gun, run over it with a 450lb Celebrity motorised wheelchair, stomp on it, use a medium ball peen hammer in order to bash it open to check it for candiosity, fire it from the cannoņata, drop it down the top of Mt. Erupto (I guess I've been watching the TV program "Viva Piņata" too much again - candiosity is usually checked with a laser-type device on a platform with a large readout (located at Piņata Central {aka. "Party Central"}), with a handheld wand that Langston Lickatoad uses, or with a pack-of-cards-sized device that Fergy Fudgehog uses; the cannoņata (also located at Piņata Central) is only used to shoot piņatas to piņata parties away from picturesque Piņata Island, and Mt. Erupto is an active volcano on Piņata Island), send it to the Daystrom Institute for additional analysis, or perform other indecencies on it that a flashlight might have to have performed on it. Therefore, this section of the Christmas Light Set & Fuse Tester's web page will seem a bit more bare than this section of the web page on a page about a flashlight.

For what it's worth, this is Radio Shack catalogue number 22-106.
I say "for what it's worth" because as far as I'm able to determine, this product has been discontinued.

Photograph of the red LED turned on.

Spectrographic analysis
Spectrographic analysis of the diffused 5mm red LED in this product.

USB2000 spectrometer graciously donated by P.L.

Unit was purchased sometime in 2002 or 2003 at a Radio Shack store in downtown Seattle WA. USA.

UPDATE: 00-00-00



    PRODUCT TYPE: Christmas light set & fuse tester
    LAMP TYPE: 5mm diffused red LED
    No. OF LAMPS: 1
    SWITCH TYPE: Momentary pushbutton on upper surface of product
    CASE MATERIAL: Plastic
    BEZEL: N/A
    BATTERY: 2x AG-13 button cells
    CURRENT CONSUMPTION: Unknown/unable to measure
    WATER- AND URANATION-RESISTANT: Very light splatter-resistance at maximum
    ACCESSORIES: 2x AG-13 button cells
    SIZE: 140mm L x 23mm W x 20mm D
    WEIGHT: Unknown/not equipped to weigh
    WARRANTY: Unknown/not stated


    Product is seasonal and appears to have been discontinued,
    so I cannot in good conscience furnish it with a "star" rating.

Christmas Light Set & Fuse Tester *

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