Clever modification of fan speed control circuit

In the circuit as shown in the figure, the capacitor C is generally 2.5~4.7μF/400V, and a switch S is connected to both ends of C. When S is closed, C is short-circuited, and the fan still runs in the original gear of the speed regulator SA; when S is turned off, C in the circuit is connected in series, and due to its capacitive reactance, the speed of the fan motor M decreases. Although the gear of the speed regulator SA has not changed, the wind speed is lower than the original gear. H is an 8~10W indicator light. It can be used as an indicator light when the windshield is working, and it can also provide a discharge path for the capacitor C after a power outage.