A brake warning lamp on the dash remains on whenever the ignition is on. If the wire to the pressure differential switch (usually a part of the combination valve or built into the master cylinder) is unplugged, the dash lamp goes out. Technician A says that this is an indication of a fault in the brake hydraulic system. Technician B says the problem is probably due to a stuck parking brake cable switch. Who is right?

Question

Quizplus · Accepted Answer

The brake warning lamp being on indicates a potential issue with the brake hydraulic system, and the fact that the lamp goes out when the wire to the pressure differential switch is unplugged supports Technician A's diagnosis. The pressure differential switch is designed to detect imbalances in the hydraulic pressure between the two halves of the brake system, indicating a possible leak or failure in the system. Technician B's suggestion of a stuck parking brake cable switch would not be directly related to the behavior described, as the parking brake switch typically triggers a separate indicator.

A Brake Warning Lamp on the Dash Remains on Whenever