# Sample Fault Diagnosis Tests

Updated 23 June 2021

## Fault Diagnosis Practice Test

These tests are used to select technical personnel who need to be able to find and repair faults in electronic and mechanical systems.

As modern equipment of all types becomes more dependent on electronic control systems (and arguably more complex) the ability to approach problems logically in order to find the cause of the fault is increasingly important.

Fault Diagnosis Test

This type of test is used extensively to select technical and maintenance personnel as well as to select for artificer (technical) roles within the armed forces.

For example, aircraft technician.

Fault diagnosis tests usually form part of a test battery in which verbal reasoning and numerical reasoning also feature.

No specialised knowledge is required to answer these fault diagnosis questions (unlike mechanical reasoning )

This sample question paper contains 12 questions and has a suggested time limit of 10 minutes.

The questions are presented in Letter/A4 format for easy printing and self-marking.

# Example Fault Diagnosis Question

There are two components to this question:

1. A grid which describes the function of a series of switches

2. A flowchart showing: input – switches – output

Each of the switches acts to alter the input before the next switch in the series.

Fault Diagnosis Test, functions, fault

This grid shows four switches and their effect on four numbered inputs which may be either on or off.

The first switch (diamond 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.

The other switches act in a similar way as detailed in the grid.

If a switch is not working then it has no effect on the input which passes through unchanged.

Fault Diagnosis Test, focal point

In this example flowchart, all of the inputs (numbered 1, 2, 3, 4) are on.

When these inputs pass through the first switch 1 & 3 are inverted (for example, switched off).

These modified inputs (1=off, 2=on, 3=off, 4=on) then pass through the second switch.

The second switch inverts inputs 3 & 4, which gives (1=off, 2=on, 3=on, 4=off).

These modified inputs (1=off, 2=on, 3=on, 4=off) then pass through the third switch.

The third switch should invert inputs 2 & 4, giving (1=off, 2=off, 3=on, 4=on).