3.5 FRONT AXLE SUSPENSION CONTROL UNIT 3. INTRODUCTION TO THE ELECTRONIC SYSTEM OF THE TRACTOR 3.5 FRONT AXLE SUSPENSION CONTROL UNIT The function of the suspension control unit is to supervise the correct operation of the hydraulic suspension supporting the front axle. When the operator activates the hydraulic suspension by pressing the pushbutton on the front console, the clearance of the front end of the tractor relative to the road surface will be controlled automatically.
With the system activated, the control unit pilots the operation of the load sensing and the up and down solenoid valves, which continue to adjust until the signal received from the position sensor corresponds to the programmed setting. At this point, the control unit deactivates the solenoid valves and the system remains active. When the position of the axle shifts due to the tractor bouncing as it moves along, the control unit responds by piloting the corrections needed to return the axle to the programmed position.
The axle suspension, used when the tractor is on the move, provides further assistance in limiting the pitching motion of the machine, increasing its stability and improving reaction in the event of emergency braking. All the control components of the system (on/off pushbutton, position sensor and solenoid valves) are connected directly to the axle suspension control unit. The only item of data not read directly by a sensor but supplied by the Infocenter, is ground speed (wheel speed), which is used to activate or deactivate the system according to the peripheral velocity of the wheels.
The suspension control unit warns the operator of any malfunction affecting monitored components, by way of an indicator light in the pushbutton. Faults are indicated using a system of coded flash sequences which, depending on how the control unit has been con- figured, will either specify the precise nature of the fault (extended alarm) or simply identify the device affected (standard alarm). The ART shows the 10 most recent alarms generated, and if a further alarm is triggered, the first of the ten will be eliminated.
To verify, using the ART, whether or not an alarm detected is “active”, the technician must cancel all the alarms, turn the starter key to the “ O ” (OFF) position, then make a fresh connection to the control unit. >?0 >? 1/ >? 1 - Front axle suspension load sensing solenoid valve coil 2 - Axle Down control solenoid valve coil 3 - Axle Up control solenoid valve coil 4 - Front axle suspension position sensor 5 - Diagnostics connector 6 - Front suspension pushbutton 4 " ( ?9& 1 1 / ! 1 / 0 4 9 20-19 >? /5/ 1 &1=1 0 11 / 14/ /= 1 1 " 614 / / 1 / 1