Turn signals (indicators) flash with the help of a relay (on older vehicles). With modern vehicles it will be electronics. The indicator circuit automatically makes the turn signals flash on and off when power is applied.
When the turn signals flash too fast, It may be because a broken lamp will have caused the indicators to flash faster (hyper flashing). But there can be other reasons. Such as replacing filament lamps with LED’s.
If you have replaced the filament lamps with LED’s, it’s likely there will be less load on the electrical circuit. The change in load on the circuit, causes the electronics (or turn signal relay) to switch on and off faster.
The video above explains why this happens, and what you can do to solve the issue…
Can be found on this page: My Turn Signal (Indicators) Flash Fast on One Side? (Opens in a new window / tab)