Fault Finding Website Example


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Our Fault Finding test is designed to measure your ability to approach complex problems logically in order to find the cause of a fault. The tests demands a high level of process thinking because you are required to identify the effect a series of switches have in altering input and output signals.

In this test there are always two parts to each question:

  • A grid that describes the function of a series of switches
  • A flowchart showing: input – switches – output.

There are a total of 7 switches that are used through the test. Each question is made up of 3 switches and each switch modifies the input before the next switch in the series. This grid shows all the functions that each switch performs:


The first switch (a triangle symbol) inverts inputs one and two. That is, if the input is on, it is turned off and if it is off it is turned on. All other switches act in a similar way as shown in the grid. If a switch has a fault then it has no effect on the input, so it passes through unchanged.

In this example question, all inputs 1-4 are off (black).

  • Switch A: When these inputs pass through switch A, inputs 1 & 2 are inverted. This gives (1=on, 2=on, 3=off, 4=off).
  • Switch B: When these inputs pass through Switch B, inputs 2 & 3 are inverted. This gives (1=on, 2=off, 3=on, 4=off).
  • Switch C: When these inputs pass through Switch C, inputs 1 & 4 are inverted. This gives (1=off, 2=off, 3=on, 4=on).

Therefore, the answer to this question is ‘No Fault’. However, if switch B had a fault then the final output would be (1=off, 2=on, 3=off, 4=on), as shown below.

Your task is to identify which switch has a fault. If a switch has a fault (i.e. having no effect on the output). In each case either a single switch has a fault or all switches are working. The test consists of 5 questions and you have 2 minutes to complete it.