Continuity check of rear brake light switch using a continuity tester

• Allof these instruments are self-powered by a battery, therefore the checks are made with the ignition OFF.

• As a safety precaution, always disconnect the battery negative (-ve) lead before making checks, particularly if ignition switch checks are being made.

• If using a meter, select the appropriate ohms scale and check that the meter reads infinity (=•>). Touch the meter probes together and check that meter reads zero; where necessary adjust the meter so that it reads zero.

• After using a meter, always switch it OFF to conserve its battery.

Switch checks

1 If aswitch is at fault, trace its wiring up to the wiring connectors. Separate the wire connectors and inspect them for security and condition. A build-up of dirt or corrosion here will most likely be the cause of the problem -clean up and apply a water dispersant such as WD40.

2 If using a test meter, set the meter to the ohms x 10 scale and connect its probes across the wires from the switch (see illustration 9).Simple ON/OFF type switches, such as brake light switches, only have two

wires whereas combination switches, like the ignition switch, have many internal links. Study the wiring diagram to ensure that you are connecting across the correct pair of wires. Continuity (low or no measurable resistance - 0 ohms) should be indicated with the switch ON and no continuity (high resistance) with it OFF.

3 Note that the polarity of the test probes doesn't matter for continuity checks, although care should be taken to follow specific test procedures if adiode or solid-state component is being checked.

4 A continuity tester or battery and bulb circuit can be used in the same way. Connect its probes as described above (see illustration 10).The light should come on to indicate continuity in the ON switch position, but should extinguish in the OFF position.

Wiring checks

• Many electrical faults are caused by damaged wiring, often due to incorrect routing or chaffing on frame components.

• Loose, wet or corroded wire connectors can also be the cause of electrical problems, especially in exposed locations.

1 A continuity check can be made on a single length of wire by disconnecting it at each end

and connecting a meter or continuity tester across both ends of the wire (see illus­tration 11).

2Continuity (low or no resistance - 0 ohms) should be indicated if the wire is good. If no continuity (high resistance) is shown, suspect a broken wire.

Checking for voltage

• A voltage check can determine whether current is reaching a component.

• Voltage can be checked with a dc voltmeter, multimeter set on the dc volts scale, test light or buzzer (see illustrations 12 and 13).A meter has the advantage of being able to measure actual voltage.

• When using a meter, check that its leads are inserted in the correct terminals on the meter, red to positive (+ve), black to negative (-ve). Incorrect connections can damage the meter.

• A voltmeter (or multimeter set to the dc volts scale) should always be connected in parallel (across the load). Connecting it in series will destroy the meter.

• Voltage checks are made with the ignition ON.

Date: 2016-01-14; view: 701