Tronair 5731, Operation & Service Instructions

Page: 22 / 119

Model: 5731
Hydraulic Power Unit
08/2016 | Rev. 08 Page | 17
8.0 TROUBLE SHOOTING
The following is a guide to solutions of common problems associated with the HPU. See related Appendices for Hydraulic and
Electrical Schematics.
If the problem is not resolved using the trouble shooting information, call the manufacturer for Technical Assistance (See
Section
1.3 Manufacturer ).
NOTE: Maintenance and Trouble Shooting are to be performed by a skilled and trained Technician.
8.1
HPU WILL NOT START
Possible Cause Solution
Supply power off ................................................................. Check incoming power and restore power. Check across-the-line
voltage on all three phase legs.
Supply power fuses are blown/ ........................................... Check and replace. Check across-the-line voltage on all three
Circuit breakers tripped
phase legs.
Control Transformer fuses blown ........................................ Check and replace.
Supply power phase or voltage incorrect ............................ Voltage/Phase Monitor Indicator light will be illuminated.
(Phase/Voltage Monitor Option H

J only) Refer to Section 3.3 Connecting Electrical Leads .
Reservoir fluid level is too high or too low ........................... One reservoir level indicator light (Low or High) will be illuminated.
(Electric Reservoir Level Option L only) Fill the reservoir above the Minimum Fluid Level arrow to extinguish
the Low Level light. Drain fluid below the Maximum Fluid Level
arrow to extinguish the High Level light.
High return fluid temperature ............................................... High Fluid Temperature indicator light will be illuminated. Allow the
hydraulic fluid to cool until the light goes out. Refer to Section 8.5
for Over-heated Causes.
Motor has tripped thermal overload device ......................... Allow the motor to cool. The thermal overload device (motor starter)
will reset automatically after sufficient cooling. The tripped condition
is usually caused by loading the motor beyond its rated capacity;
however, any condition (such as unbalanced voltage) that causes
an increase in amperage can result in a tripped condition.
NOTE: Using the bypass valve to meter flow or pressure will increase the motor load and may cause the thermal
overload device to trip. Refer to section 5.5.4 Bypass Valve Operation for proper use of the bypass valve.
8.2
NO FLOW
Possible Cause Solution
Motor turning in wrong direction .......................................... See Section 3.3 Connecting Electrical Leads.
Flow control set too low ....................................................... Increase flow setting.
Fluid level in reservoir too low ............................................. Service the HPU reservoir.
Air in pump inlet lines .......................................................... Disconnect the HPU from the aircraft. Fill the HPU reservoir to a
level above the pump inlet port. Set the reservoir selector valve to
the HPU Reservoir position.
Fully open the Bypass Valve. Close
the Pressure and Return ball valves at the rear of the unit. Adjust
the pump flow to maximum and "bump" the start and stop switches
to "jog" the motor. Flow should be indicated at the Flowmeter on
first or second "jog".
NOTE: Under some conditions where a large amount of air has entered the system, the pump may not be able to
draw an initial prime. If this occurs, loosen the inlet hose near the pump and allow air to escape. Re-tighten the hose
when fluid appears.
Motor is turning but pump is not .......................................... Check pump and motor couplings to ensure they are tight.
Flow path does not exist ...................................................... A flow path (such as a moving actuator or an open circuit) must
exist for flow to be present. When system pressure exceeds the
compensator control setting, or when the system no longer requires
flow, the control de-strokes the pump while maintaining the preset
pressure.