built said:
Can you explain to me why you put the test light ends to both sides of the fuse clips and how that tells you of a short circuit?
thanks.
In your example of the dome light, the 12 VDC + comes from the battery to the fuse block, through the fuse, then the bulb in the dome, to the door switch to ground. When you replace the fuse with the test light, one lead is to 12 VDC + and the other to ground. If the swtich is open, you have no circuit and the test light is not lit. If there's a short to ground, you complete the circuit and the test light lis lit.
The dome light is not a good example because the door switch is last in the circuit before the ground.
If the door is closed, the bulb is
not in the dome light and the test light is is not lit, it should not light if you open the door. If it does, there's a short across the dome light itself to the switch. If the test light is lit with the door open or closed, the dome light feed is shorted to ground.
If the ignition is off, and the circuit you're testing is "hot" at all times, the switch to that accessory is "off" and the test light is lit, that tells you is that there is a short to ground between the test light and the switch in that circuit. If the switch for that circuit is "off" & you blow the fuse when you turn it "on", you have to disconnect the battery and start checking for shorts in the rest of the circuit with a continuity meter. If the circuit is "hot with ignition on", the switch for the accessory is "off" and the test light is lit, there could be shorts anywhere between the fuse block, the steering column on to the accessory's switch.
I know that's a lot to swallow. Electrical troubleshooting's a lot easier to do than to explain.
Tommy