CD. Checking of Wiring

CD. Checking of wiring

Many faults in the electrical system are the result of faults in the wiring and connections. These faults arise primarily through interference from other electrical systems, mechanical or chemical effects.

Check connections optically CD1.
Break in circuits CD2.
Short circuit to earth CD3.
Short circuit between wires CD4.
Resistance in switches and connections CD5

Intermittent faults.
When intermittent faults arise, the cause is often in the wiring and connections. Check them according to the instructions below.

CD1




Check the connectors visually
In all measurements and checks in which the connectors are taken apart. Examine the connectors carefully.

Check:
- Look for signs of oxidation which may affect the contact in the connections.
- Ensure that the the connector tabs are undamaged and that the copper conductor maintains proper contact with the tab.

CD2




Break in the circuit
A break in a circuit can be discovered if one of the functions fails to work properly.
Chafed and torn-off wires and poorly connected wires are the usual cause of breaks.

Check:
- Disconnect the connectors at both ends of the wire.

Measure both ends of the wire using an ohmmeter. The ohmmeter should show approx. 0 ohms on a wire without any break.

CD3




Short circuit to earth
A short circuit between a live wire in a circuit and the earth is usually discovered when the fuse goes as soon as current is applied to the wire.

Check:
- Activate all the switches and sensors in the circuit and check it the fuse goes.
- Shake the wires lightly and pull gently on the connectors during measurement to locate the source of intermittent faults.
- Disconnect connectors from components in the circuit so that they do not affect the measurements.




Measure using an ohmmeter between wires and earth to locate possible short circuits to earth.
The ohmmeter should indicate infinite resistance if no components are connected.

CD4




Short circuit, between wires
Short circuit between wires will not always cause a fuse to go. A fault is usually discovered when a particular function fails.

Check:
- Shake the wires lightly and pull gently on the connections during measurement to locate the source of intermittent faults.

1. Measure with a voltmeter at various points in the circuit at the same time as switches and sensors are activated.
The voltage shown by the voltmeter depends on the position of the switches and sensors. Use the electrical wiring diagram to determine the correct voltage in the circuit.

2. Measure with an ohmmeter between suspected wires to locate short circuits between them.
The ohmmeter should show infinite resistance upon measurement between wires which are not connected to each other in the circuit.

CD5




Resistance in contacts and connections
Resistance in contacts, wires and connections should really be 0 ohms. However, there is always a certain resistance owing to poor connection between wires, oxidation of connectors, and wear.
If resistance is excessive, the result is impaired function. The degree of resistance which is permitted before function is impaired depends on the load on the circuit. A general guide is a few ohms.

Check:
- Shake the wires lightly and pulley gently on the connections during measurement to locate the source of intermittent faults.




- Test with a loose male tab to check that the female tab offers proper contact and that there is firm contact even if the male tab is pulled gently away.

Measure with an ohmmeter between the ends of the wire.
Measure also with the switches and sensors connected to identify excessively high contact resistance.
The ohmmeter not show more than a few ohms on a circuit with an acceptable resistance in contacts and connections.