Scooter lights not working

The problem it solves

Lighting faults get fixed by replacing bulbs until something works. That succeeds often enough to feel like a method, and it misses the two faults that actually matter: a bad earth, and a charging system overcharging and blowing bulbs faster than they can be replaced.

The first question splits the problem cleanly and costs nothing. If one light is out, the fault is in that light's own branch — its bulb, its holder, its earth, its switch. If everything is out, the fault is upstream of all of them, which is a fuse, a supply or a shared earth.

Dim rather than dead is a third case and points somewhere different again: resistance somewhere in the circuit, usually a corroded earth or a connector, dropping voltage before it reaches the bulb.

And bulbs that keep blowing is a fourth, which is not a lighting fault at all — it is a charging fault, and replacing bulbs will continue to be expensive until the regulator is dealt with.

The mistakes this sheet exists to prevent

• Replacing bulbs repeatedly without asking why they keep failing.
• Checking the bulb and the switch but never the earth, which is where a surprising share of these live.
• Assuming a bulb is good because the filament looks intact — it can be broken invisibly at the base.
• Fitting a higher-wattage bulb to cure dimness, which loads the circuit further and melts holders.
• Ignoring one dim light when the others are fine, which is a textbook bad earth on that branch.

How to use it

1. 01Establish whether it is one light or all of them before touching anything.
2. 02Check the earth on that light's branch before condemning the switch.
3. 03If bulbs keep blowing, stop replacing them and check the charging system.
4. 04Record what you found, including what came back normal.