How to Find an Electrical Draw, or a Short on Your Vehicle.

By | May 11, 2019

How to find a electrical short on most vehicles. This process was completed on an older make and model, but it is the same concept with any type of vehicle. I will do another write up and another video on a newer vehicle to show in detail how to complete it. If you are not mechanically inclined, I will explain it in detail here so you will get the just of it.

The only tool you will need is a test light. You will be pulling fuses and the fuse puller provided by car manufacturers are sometimes difficult to use, especially when pulling a lot of fuses as this will require. I prefer a pair of needle nose pliers. So in my case, I used two tools, the needle nose pliers and a test light. Any kind of 12 volt test light will work. I have noticed the LED style is best because it can light up on the smallest amount of voltage. I have also used a volt meter. When using a volt meter, put it on the smallest setting.

Test light

One … Disconnect the battery terminal and put it aside. While performing this test, one of the battery terminals will not be connected to the car. The choice is up to you, it does not matter, I use the one that is closest to the fender when working by myself (or fuse panel) so I can see the light go out. I will explain that shortly.

Disconnect battery terminal

Two … Attach the the test light to the the battery or terminal that you removed. The direction on the test light to terminal or battery does not matter either. As long as the test light is connected to the battery and the terminal you removed.

Attach test light

In the next two pictures, I had the positive cable removed. I placed a spare terminal on the post that is not connected to anything. I clipped the wire end of the test light to the terminal then removedĀ  the sharp end of the test light and stuck it onto the positive side of the battery and the extra terminal that was on the post of the battery enabled me to be hands free. It supported the test light so I did not have to hold it.

Positive terminal removed

Spare terminal

The light immediately came on. This tells me something in the truck was drawing power. Now to find the problem.
Remember the terminal is disconnected and the test light is now making the connection from the battery post to the battery terminal.

Three … Locate your fuse panel. Your vehicle may have a couple of them, under the hood, under the dash, side of the dash, or in the glove compartment. Check your vehicles hand book if necessary.

Fuse panel

Four … One by one pull a fuse and look at the light. If you can not see the light, you may need a helper to relay the information to you on whether the light is on or off. If the light is still on, put the fuse back and go to the next fuse. Do this over and over until the light goes out.

Pull fuses

Make sure of a couple things, your dome light is not on while performing this test or your radio is not on.
You can not have anything on while performing this test. If you must leave the door open to get to the fuses and the dome light is on, you can remove the dome fuse or remove the dome light bulb itself. This will break the connection of power draw and not confuse you to the issue. When you come to the fuse that makes the test light go out, you have narrowed your search to almost nothing. Let’s say your cigarette lighter fuse makes the test light go out.

Check test light

Then the cigarette lighter wire is touching ground some where. You have narrowed your draw to one wire on the vehicle. Lets say the light goes out when you remove the brake light fuse, then you have a brake light wire shorting out. You will still need to locate the wire that is grounding but you will narrow this search to one wire. This whole process takes only about 15 minutes to perform and it gives you so much information. I will post a step by step video here below, click the link for that video.

 

12 thoughts on “How to Find an Electrical Draw, or a Short on Your Vehicle.

  1. Leslie H Brown

    Hi Brian, Great video, my problem is a little different, my test light comes on but gos out instantly, take the probe off for a couple of seconds put it back on and same thing, comes on and gos off. any help would be great.

    Thank you
    Les Brown

    Reply
    1. Brians Garage Post author

      It could be your ECM powering up from the grounding of the test light. It sounds like you do not have an issue with your battery draining.

      Reply
    2. Jose

      Hi Brian , great video. My problem with trying to find the issue is my battery is located on the trunk of the car. It is a 2007 Chevy cobalt. I tried removing the fuses but with the trunk open the light comes on

      Reply
      1. brian

        locate the fuse for that light and remove it. that will eliminate any draw from that circuit and you can continue with the test.

        Reply
  2. Eric

    2006 cts cat brake light’s not working what could be the problem

    Reply
  3. 3r1c

    Oh-One Durango SLT: Passenger side brake light with new bulb, good fuse doesn’t work. Tester doesn’t show power to it. That’s a long way to chase a wire down, and a lot of panels to remove. Can I jumper from the driver’s side like a redneck and feel reasonably safe that the NM State Gestapo won’t stop me for a brake light out despite the left and top-center lights working?

    Reply
  4. Tlm

    Done this on my 94 keep Grand Cherokee the test light goes out when the fuse is out of the power distribution that says fuse block battery feed.

    Reply

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