原帖由： Eric Viitala ,
@vladsc50 , The brake light in the instrument cluster will light up when the balance of pressure from the front brake system to the rear brake system. In the lines leading from the master cylinder, there is a pressure differential valve. PRESSURE DIFFERENTIAL VALVE The pressure differential switch is connected to the brake warning light. The switch is actuated by movement of the switch valve. The switch monitors fluid pressure in the separate front/rear brake hydraulic circuits. A decrease or loss of fluid pressure in either hydraulic circuit will cause the switch valve to shuttle to the low pressure side. The movement of the switch valve lights the brake warning lamp. Once the pressure equals out the switch will return to normal. This will probably require bleeding the front and back brake hydraulic circuits. Be careful not to let the fluid in the master cylinder run out when bleeding, as that will introduce air into the system at the very beginning and will be very difficult to remove. When you are done bleeding the light should go out. If not, the pressure differential valve may need replacing. Hope this helps.