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How to Find a Short Using Resistance

Electronics involves the combination of two or more electronic components on a circuit board which then manipulate or regulate electricity to complete a specific task. All electronic components, except for the capacitor, have a given resistance value when being measured with an Ohm meter or a multimeter set to measure resistance in Ohms. When components such as these fail, two wires inside come into contact with each other, bypassing the resistive compound within and then appear as an electrical "short." To find a short, one must only know how to read an Ohm meter or a multimeter.

Things You'll Need

Multimeter with set of test probes
Solder
Soldering Iron
De-soldering wick

Instructions

- 1
  Unplug the electrical device from its power source, generally a wall outlet or a battery. Remove the cover from the machine or device to expose the electronics within.
- 2
  Locate the electronic component assumed to be causing the difficulty. This step will require extensive troubleshooting and trial and error in some cases. Once the suspected component has been found, look up information about that component, which includes maximum power rating and what its normal resistance should be. This information is always found on the schematic diagram for the device being worked on.
- 3
  Plug in the soldering iron and bring it up to full operating temperature. Unroll a small amount of de-soldering wick and lay the tip of the wick onto the solder joint on one end of the component. Touch the hot iron tip to the top of the de-soldering wick, just over top of the solder to be removed. Heat until you see the solder turn to liquid and it is being absorbed by the de-soldering wick. Quickly lift the soldering iron tip and the de-soldering wick away from the circuit board and then lift the components wire out of or off of the circuit board.
- 4
  Turn on the multimeter and set the meter to measure resistance in Ohms. Use the next-higher setting closest to the normal resistance the component is supposed to have by rotating the dial to measure that amount of resistance.
- 5
  Touch one of the probes to the components wire that is still soldered onto the board and then touch the other probe to the wire of the component on the other end that is now disconnected from the circuit board.
- 6
  Observe the reading on the multimeter screen and make a note whether there is a given resistance number, such as 2400, all zeros or an infinity indicator, which is a number one followed by a decimal (1.) If the resistance reading shows an actual number value that is close to what the component should have, then the component is in good shape, and further troubleshooting is necessary. If the readout shows a series of zeros, then the component is damaged and shorted and must be fully removed and replaced. If the reading is a 1. then there is a possibility that the component is "open" and needs to be replaced.

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