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How to Make a Car Fuse Tester and A Quick Voltage Indicator

By on October 12, 2015
car fuse tester








In the following five steps you will have a fuse tester and a quick voltage indicator for cars

STEP1: What you need:

test pen

1- One neon tester for line voltage screw driver shape /with bigger compartment is better. Shown in the above photo

2- 50 cm wire no 2/5

3- A roof lamp of KIA pride car and/or slimmer one this is depend on your neon lamp tester compartment/top and bottom of the lamp must be metallic

4- Extra  spring  small one. You may also use the spring of neon tester as well. By pulling the spring from two side you will have bigger and stronger spring for this project

5-Wire clip



car voltage tester

You have to open the back holding cap of neon tester. And you won’t need the neon lamp and the assembly because it won’t work with the car DC 12 volt.

Step 3:

how to make car fuse teter

You have to make a hole in the back cap with drill no 2.5 to let the wire of tester  go through.

Step 4 :

Assembly of tester has six steps:

One.  Place the lamp inside the compartment of tester.

Two.  Let the wire go through the cap that you drilled before and.

Three. Hook the wire to big spring ( I have to mention  that is not require to solder but if you solder it is better)

Four. Place the spring inside the compartment

Five. Do not forget the cap, this must be keep close  everything

Note : spring must be strong enough to keep the head of the lamp in good contact with the end of the screw driver that is present in the bottom of compartment

Six. solder the other end of wire to wire clip

project is completed.


By clipping the wire clip to body of the car (in most cars the chassis of the cars are the negative side of the buttery ) you attached to negative side of the circuit if the  voltages  are excite in your testing point  by touching the end of the probe of your tester the lamp will glow and indicate the continuity of circuit and or presence of voltage.

For testing the fuses just clip the wire to the any metallic surface of car and by touching the fuse if the fuse is intact the lamp will glow otherwise the fuse is gone do not forget that fuse has 2 contact in back side both contacts must fire the lamp otherwise the fuse is bad

a car fuse

testing car fuse

 Testing the tester on car battery-it should should be very bright

NOTE: I made this project with help of the LEDs but I personally prefer this tester with of 12 dc lamp of the car due to the following reasons:

1) The illumination of car lamp is much stronger than LEDs especially cars are being tested out door (under sunlight) to see the light of LEDs are difficult.

2) In LEDs, the polarities – + must be observed otherwise tester will not work but in lamp style no polarities is required to be observed.

Enjoy car repairing.






This article was prepared for you by Mr Beh from Iran.

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If you want to know more about car electronics repair you can click on the below photo:

car electronics repair


Note: You may check out his previous repair articles in the below link:



  1. Albert van Bemmelen

    October 12, 2015 at 1:34 pm

    Nice work Mr Beh. You also could add a small 12V Buzzer to your tester. But that probably will not fit into your previous Neon AC tester.

    • beh

      October 12, 2015 at 5:13 pm

      Hi Albert
      yes is a good suggestion but as you told needs a bigger compartment
      and thanks .

  2. Robert Calk

    October 12, 2015 at 2:18 pm

    Good job, Beh. In my tester I have a red & green LED that lights good.

  3. beh

    October 12, 2015 at 5:18 pm

    Are the light of LED S strong enough for work on car out doors?

    • Robert Calk

      October 13, 2015 at 2:47 am

      Sure, it was good to about 22 volts if I remember right.

    • Robert Calk

      October 13, 2015 at 4:25 am

      Sorry Beh, It is called, "Low voltage polarity checker". Here is the link:
      It's just Ohm's Law: A car battery is 12 volts. An alternator usually put's out about 13.5V. If we use a 1K 1/2W resistor, 15V would give us 15mA at 0.225W. Most 5mm LED's will handle 15mA easily.

      • beh

        October 13, 2015 at 6:22 pm

        HI ROBERT
        I know for you and in your country to have this tester is easy in K MART or WALMART you may find these tester very cheap and in different type s but in my country or countries like me it is difficult to find such tools and is a challenge . and all your calculations are correct but still i have problem to find some thing to carry the led or the lamp that is why i found that screw driver to make this tester this tester is good for poor countries not like yours and thanks for your supporting comments regards beh

        • Robert Calk

          October 14, 2015 at 11:22 am

          Hi Beh, WalMart is a poor choice for electronic components and I never go there for that. I just used 2 common 5mm LED's, a 1K 1/2W resistor, a set of cheap leads, a plastic piece of straw, and some hot glue to seal the ends. I figured that people in poor countries could find the parts and build a checker like mine cheaper and easier than that type. In stead of the leads, they can just use some wire and croc clips.

          • beh

            October 15, 2015 at 5:49 pm

            Hi Robert
            yes this is correct by using a peace of wire and a lamp or led alsois possible to make this experiment i just wanted to give a shape and collect all the parts together this idea is not new i am sure just like my tester must be find in web for sale i mean factory made .i hope you accept my tester cos you can find this faz tester all around the world and the rest is easy . when i was in USA K MART was not bad but since that time many years is passed and for sure you know better than me and regards beh

            • Robert Calk

              October 15, 2015 at 7:11 pm

              Hi Beh,
              I'm sure your tester type will appeal to some people. Good job and thanks for the article.
              WalMart and such have some cheap stuff you can buy for automotive and stuff, but they don't have individual components. They might have a screwdriver type test light, but I would trust the one I built any day before I would trust theirs. I do have store-bought 120V mains checker, but I don't remember where I bought it - I've had it a long time.

              • Gary Gemmell

                January 5, 2016 at 5:41 pm

                Nice one Mr Beh!

                It appeals to me and I am in Scotland the land of the tightarse!

                I have already made up Mr Beh's tester and it works a treat - much easier to use than my multimeter!

                Thanks Mr Beh you have a happy customer!!!!
                We dont have K-Mart only Halfords and its very expensive probably $20.
                You save me $20 I owe you beer (many)!!!

  4. Anwar Shiekh

    October 12, 2015 at 8:03 pm

    Can one not use two LEDs, wired oppositely, so at least one lights?

    • Robert Calk

      October 13, 2015 at 2:44 am

      I did in my article, "Low voltage polarity tester". When testing AC, both LED's will light up. I guess you missed it.

      • Robert Calk

        October 13, 2015 at 4:33 am

        Here is the link:

  5. Andre Gopee

    October 12, 2015 at 10:16 pm

    Nice job Beh, but in my country these testers sell for Dog cheap. You can pick one up for around TT$5.00 that is around US$1.00

    • beh

      October 13, 2015 at 5:05 pm

      Hi ANDRE
      Where are you from ? no in my country you can not find such tester
      also not the parts for LCD S and LED S TV .that is why i start to make one. you know i love tools and if this tester is this much cheap in your country send me one MR yong has my address . and make me thankful of yourself

  6. Mark

    October 13, 2015 at 5:37 am

    Hey Beh,

    Thanks for an informative article. These globe styles can be very helpful for testing fuses.
    However, with electronics being so sensitive now-a-days, it is important to use LED style test lights when working with electronic components. Here is an article on one I made for a workmate earlier this year, using bipolar LEDs. They are bright enough to see in the daylight.
    Keep up the good work. I always enjoy your articles.

    • beh

      October 13, 2015 at 4:59 pm

      Hi Mark
      yes i read your article and really is useful but my question is from where i have to find that cylindrical shape compartment to install the the leds inside that was my problem and i found this tester screw driver
      and i convert it to fuse tester

  7. Ulises Aguilar Pazzani

    October 13, 2015 at 10:21 am

    Mr Beh very good idea

  8. Humberto

    October 15, 2015 at 9:29 pm

    A good and cheap project beh. Thanks and keep up.

  9. beh

    October 17, 2015 at 11:27 am

    Hi Humberto
    you are welcome and thanks for supports .


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