Hydraulic System Troubleshooting - Blue Bird Q - BUS Owner's Manual

uses a portion of the vehicle's hydraulic service brake system to provide additional brake holding action.
WARNING: If a system leak develops, discontinue use of the Door/Brake Interlock until the cause of the
malfunction is diagnosed and corrected
WARNING: Brake lock and warning circuits are disabled if battery power is lost or disconnected.
Read Warnings and Operating
Instructions prior to using.
690 Brake Lock
TO LOCK:
1. Set parking brake
2. Move lock switch to ON position
TO RELEASE:
1. Move lock switch to OFF position
2. Release parking brake
HYDRAULIC SYSTEM—TROUBLESHOOTING
1. Hydraulic fan will not run.
A. Check hydraulic oil level in reservoir. (Sight glass)
B. Check fan motor for free rotation, fan motor should rotate freely. If not rebuild or replace fan
motor.
CAUTION: Engine should be shut off when checking fan motor for free rotation.
C. Disconnect wires from relief valve solenoid or temperature control switch, and start engine. If fan
runs with wire disconnected, the temperature control switch is at fault. Replace switch. If fan does
not run with wire disconnected, the solenoid valve may be at fault. Repair or replace solenoid
valve. If this does not correct the problem proceed with the following steps.
D. With hydraulic system at normal operating temperature check pump output pressure to specifica-
tions below. Check pressure with wires disconnected from relief valve solenoid, or temperature
control switch.
Note: A pressure tap can be installed at port marked "PR" on the relief valve.
ENGINE
5.9 Cummins
8.3 Cummins
E. If pressure is low, adjust the pressure relief adjustment screw by loosening the jam nut and turn-
ing the adjustment screw clockwise to increase pressure. If the pressure comes up to specifica-
tions, and the fan speed doesn't, the fan motor has excessive internal leakage and is at fault. Repair
or replace fan motor. If specified pressure is obtained, the relief valve is at fault. Repair or replace
relief valve.
Serious injury
or death can
occur if these
instructions are
not followed.
Vehicle equipped with Brake Lock System.
Operator must read and understand operating
instructions before using vehicle.
Brakes will release if ignition is turned off when
Brake Lock is remotely activated.
Do not use Brake Lock in place of original
equippment parking brake.
Always set parking brake and use wheel chocks
and outriggers with Brake Lock.
Do not use Brake Lock for overnight or prolonged
parking.
Release Brake Lock before moving vehicle.
Brake Lock and warning circuit are disabled if
battery power is lost or disconnected.
PUMP PRESSURE (PSI)
100-300
2000
2450
WARNING
PREVENT
ROLLAWAY
ENGINE RPM
800
2500
2400
53
WARNING
Serious injury or death can occur if
these instructions are not followed.
Opening vehicle service door causes
brakes to be applied.
Vehicle equipped with Door/Brake Inter-
lock.
Operator must read and understand oper-
ating instructions before using vehicle.
Brakes will release if ignition is turned off
when Door/Brake is remotely activated.
Do not use Door/Brake for overnight or
prolonged parking.
Close vehicle service door before moving
vehicle.
Door/Brake and warning circuit are dis-
abled if battery power is lost or discon-
nected.
FAN RPM
200
1900
1950