Terex T780 - Air Pressure

Parking Brakes
MAXI-BRAKES WON’T APPLY (From Park Brake Button)
CAUSE REMEDY
Restricted hose or tube Remove restriction or replace
Defective relay valve Repair or replace
Defective spring brake valve Repair or replace
Defective control valve Repair or replace
MAXI-BRAKES WON’T APPLY (With loss of air pressure in one service reservoir)
CAUSE REMEDY
Restricted hose or tube Remove restriction or replace
Defective control valve Repair or replace control valve
BRAKES WON’T APPLY ON REAR AXLE (With loss of air pressure in one service
reservoir)
CAUSE REMEDY
Restricted hose or tube Remove restriction or replace
Defective spring brake valve Repair or replace spring brake valve
MAXI-BRAKES WON’T RELEASE
CAUSE REMEDY
Control valve not pushed out Pull in
Insufficient system air pressure Allow engine to run to increase pressure to
above 70 p.s.i.
Restricted hose or tube Remove restriction or replace
Insufficient hold off pressure Check for system (or excessive valve) leaks
Leaking brake actuator diaphragm Replace brake actuator (spring pot)
Defective relay valve Repair or replace relay valve
Defective spring brake valve Repair or replace spring brake valve
Defective control valve Repair or replace control valve
403P/N 12261-683 REVISED: January 2015