Technician A says that the pressure differential switch may need to be re-centered after bleeding the brakes. Technician B says that there are several types of pressure differential switches, and each requires a different method of re-centering. Who is correct?
a. Technician A
b. Technician B
c. Both Technician A and Technician B
d. Neither Technician A nor Technician B

The pressure differential valve is the equipment that warns you if you leak one of your brake circuits. After draining and refilling some brake system pressure differential switch may be actuated and an indication light may be illuminated. If the indication light sojourns sparked after draining the valve piston may demand to be re-centered. If the pressure is replaced to the brake line and your brakes appear to be running accurately over, then the reset button operated.

The common practical method to re-center the piston is to fix the failure, drain the system and then generate a pressure loss opposite what moved the piston in the first place. Each type has a unique kind of re-centering technique.