Brake Fluid Level Switch

The brake fluid level switch is mounted in the master cylinder reservoir, and is hardwired to the ABS module through a signal circuit and a separate return circuit. The ABS module provides a reference voltage to the brake fluid level switch. When the brake fluid level is low, the float drops, allowing the switch to close, pulling the reference voltage low. When the brake fluid level is high, the float lifts, opening the switch contacts, sending the reference voltage high on the signal circuit to the ABS module.