The electrical fault tracing advice thread

[Owen92]

I seem to keep giving the same simple advice out about basic fault tracing, so here's a thread that we can all add our knowledge to.

Bulbs

If a light is out, check the bulb! A bulb can go at any time, even just after fitting. Even if two go at the same time, check the bulbs first as this will let you know if there is a fault or not.
If the bulb is ok, check the fuse.
If the fuse is good, test the voltage at the bulb holder. If there is no voltage. then consult a wiring diagram to further fault trace.

Fuses

Fuses are only there to protect the circuit from a high current. Once they blow, they break the circuit until the fuse is replaced. So if your fault is intermittent, the fuse is ok.
Do not put a higher rated fuse in!!

Washer jets inoperative

First thing is to make sure there is washer fluid in the washer reservoir.
If this is ok then check the fuse.
If fuse is ok then check voltage into the washer motor.
If voltage in is ok, then remove the washer pipe from the washer motor and operate the washers. If no fluid is being pumped through, the washer motor is faulty.

Rear lamps dimming with indicators / operating with other lights

This is almost always an earthing fault.

 

[AdDaMan]

For the washer jets you need to add the the actual jet nozzle needs to be checked with a pin for blockages.