indicated, or other systems fail to operate, troubleshoot main
hydraulic system. If the hydraulic control panel pressure gage
indicated sufficient system pressure and other hydraulic systems
operated, continue troubleshooting.
o Attempt to open and close the upper rear door first with the top
upper rear door switch, then with the bottom upper rear door
switch (Fig. 50). If only one of the switches opens and closes
the door, you must troubleshoot the electrical system.
the problem is not electrical and continue to troubleshoot
Upper Rear Door Switches.
o Manually operate the upper rear door directional control valve
with the override buttons located at both ends of the valve (Fig.
51F). If the valve sticks or does not return to center, replace
the directional control valve. If the valve operates correctly,
and the upper rear door opens and closes, you must troubleshoot
the electrical system. Assume the valve operates correctly but
the door does not open or close and continue to troubleshoot the
o Hold the upper rear door switch in the UP position and slowly
open the dump valve (Fig. 52F). If the door does not open, shut
down the hydraulic system. Remove the inlet and outlet hydraulic
hoses from the tee connectors and install a tee connector and
pressure gage between the inlet and outlet hoses (Fig. 53).