Melted headlight connector

[Catnapper]

Just replaced the headlight connector on my Thundercat. Now when on dipped beam it appears there is a slight current getting to the main beam cable as the main beam light indicator glows very dimly only when the bulb is plugged in.
It doesn't glow when bulb not in.
Any ideas
TIA

[gareth_r]

Weird electrical stuff is often the result of a bad earth connection.

[thatdude]

Trace the wiring back to a common oint - a connector, most likely. You might find some corrosion causing shorting across the terminals, or some chafed wires touching.

Also inspect the headlight switch / main beam switch circuit - again, looking for areas where there is corrosion causing shorting etc.

You might like to get hold of a multimeter to run some tests (resistance, current, voltage) at various points in the circuits and you can track down where the issue is.

[Catnapper]

thatdude said:

Trace the wiring back to a common oint - a connector, most likely. You might find some corrosion causing shorting across the terminals, or some chafed wires touching.

Also inspect the headlight switch / main beam switch circuit - again, looking for areas where there is corrosion causing shorting etc.

You might like to get hold of a multimeter to run some tests (resistance, current, voltage) at various points in the circuits and you can track down where the issue is.

Cheers,
The only query I have to tracing it all is that it only glows when the bulb is connected. Everything is fine without the bulb. Going through all settings of the light, dipped/main beam, flash etc.
Does connecting the bulb draw extra power from somewhere? Or is it a dodgy connector block.
TIA

[Steve Bass]

Catnapper said:

thatdude said:

Trace the wiring back to a common oint - a connector, most likely. You might find some corrosion causing shorting across the terminals, or some chafed wires touching.

Also inspect the headlight switch / main beam switch circuit - again, looking for areas where there is corrosion causing shorting etc.

You might like to get hold of a multimeter to run some tests (resistance, current, voltage) at various points in the circuits and you can track down where the issue is.

Cheers,
The only query I have to tracing it all is that it only glows when the bulb is connected. Everything is fine without the bulb. Going through all settings of the light, dipped/main beam, flash etc.
Does connecting the bulb draw extra power from somewhere? Or is it a dodgy connector block.
TIA

Most likely a potential differential. Same logic applies to the alternator light in cars where the voltage floats and the light goes out when the ground side rises to the same potential as the feed side.
So look for a common earth connector to the frame and take it off and clean the frame tab, the loom tab etc.
Another way to check is to run a temporary ground cable from the -ve of the battery to the ground post. If the light then goes out, you've found the problem.
Also check if the loom earth point is directly to the frame or connected to a fairing/headlight sub-frame (for example) and that unit's connection ot the main frame is poor.
As said above, 99% of weird electrical faults are due to poor earths setting up floating potentials between components on the bike.

Edited by Steve Bass on Thursday 14th May 12:56

[Catnapper]

Reconnected old connector light main beam indication light doesn't illuminate. Happy days. Earth melted on it.
Reconnect new one, indication light back on. Ran an earth from connector to battery still lit. Guess it means more hunting down this dodgy earth.