The left indicator flashes rapidly while the right side flashes normally.
The flasher is load-sensitive and one lamp on that side has failed.
Suggested test plan
- Identify the dark lamp.
- Verify pulsed supply at the socket.
- Replace the bulb and re-test the flash rate.
- Check earth if the new bulb still does not work.
Safety: 12 V systems are low voltage but can still cause burns and fire. Disconnect the battery before working on wiring and never short a battery terminal.
Load-sensitive flashers are a built-in diagnostic: fast flash points to a missing load on that side.