Adjusting The Automatic Throttle Control; General Description - Husqvarna PP 418 Manual De Instrucciones

ADJUSTING THE AUTOMATIC THROTTLE

GENERAL DESCRIPTION

The AUTOMATIC THROTTLE function is triggered by an
adjustable pressure switch located on the hydraulic mani-
fold.
A. Throttle Control Pressure Switch
B. Pressure Relief Valve
When the fl ow selector is set to (for example) 40 liters (10
gal), that amount of oil will circulate through the hoses and
through the tool and back to the tank.
The circulation of the oil through the hoses creates a
small pressure (known as "back pressure") at the pressure
switch.
The back pressure in the system can vary for many re-
asons such as;
• Cold hydraulic oil
• The length of the hoses – a longer hose creates more
back pressure.
• The valve in the hydraulic tool can have a high restric-
tion.
In some applications the hydraulic system restriction may
be too low. This will cause the engine to remain at idle
speed even after the tool is engaged and full power is
required.
When a trigger is activated at the tool, the oil pressure
quickly rises to in excess 50 bar (700 psi). This normally
triggers the AUTOMATIC THROTTLE control to increase
the throttle to "FULL". It is desirable that the engine enga-
ges to full throttle immediately when the tool is activated.
ADJUSTMENT
On the PP 418 the threshold pressure at which the throttle
reacts can be adjusted to reach a desired function for a
specifi c tool and condition.
Step 1
Hook up the hoses and tool to be used.
A B
Step 2
Turn the AUTOMATIC THROTTLE switch to the ON posi-
tion.
Start the engine and let it idle for 1 minute. The engine will
now idle at 1900 RPM.
Step 3
Turn the FLOW SELECTOR to the proper setting for the
tool.
Note: If the oil is cold the back pressure in the system can
trigger the full throttle function.
Step 4
Let the hydraulic oil warm up for one or two minutes. It
is now OK to start the work. The hydraulic oil will reach a
stabilized operational temperature in approximately 5 to 10
minutes.
Step 5
If the machine has been operated for 10 minutes and the
AUTOMATIC THROTTLE function is not working correctly
the pressure threshold value between the idle and full th-
rottle function can be adjusted.
NOTICE: The Throttle Control Pressure Switch setting has
NO impact on the relief valve setting (= maximum sys-
tem pressure). It is strictly sensing the system pressure to
signal the controller to operate the engine at Idle or Full
Throttle. DO NOT adjust the pressure relief valve.
Use an 8 mm or 5/16" hex key to adjust the throttle thres-
hold pressure.
Scenario 1
With the Automatic throttle switch in the ON position, the
engine will stay at FULL THROTTLE even when the hydrau-
lic oil is hot.
Adjustment Turn the Adjustment Screw - Clockwise in
1/8 turn increments until proper function is
achieved.
Scenario 2
The engine will remain at IDLE SPEED when the tool is
engaged. It might work OK when the oil is cold.
Adjustment Turn the Adjustment Screw - Counter
Clockwise in 1/8 turn increments until
proper function is achieved.
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