Tech Tips
Service Call:
Emergency outrigger interlock over-ride
Tools Required:
None
Model(s):
All Digger Derricks or Aerial Devices
with an outrigger interlock system

Tech-Tip 73 Rev. A

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Released: 12/6/2018

Tech Tips
Tech Tip Safety Rules
Danger
Failure to obey the instructions and safety rules in the appropriate
Operator's Manual and Service Manual for your machine will result in
death or serious injury. Many of the hazards identified in the operator’s
manual are also safety hazards when maintenance and repair
procedures are performed.
Do Not Perform Maintenance Unless:
• You are trained and qualified to perform maintenance on this
machine.
• You read, understand and obey:
o manufacturer’s instructions and safety rules
o employer’s safety rules and worksite regulations
o applicable governmental regulations
• You have the appropriate tools, lifting equipment and a suitable
workshop.
The information contained in this tech tip is a supplement to the service
manual. Consult the appropriate service manual of your machine for
safety rules and hazards.

Tech-Tip 73 Rev. A

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Released: 12/6/2018

Tech Tips
Overview

If the outrigger interlock on a digger derrick or
aerial device malfunctions, the boom may
become inoperable and remain in the air.
This emergency procedure can be used to
override the interlock to stow the booms for
transport and repairs.

Precautions

Determine if the aerial device or digger derrick is
energized or in close proximity to energized
power lines. If it is, precautions must be followed
before ground personnel can approach or make
contact with the vehicle. The use of insulating
mats, shoes, or gloves may be required. Follow
your company’s procedures before approaching
or touching the vehicle.
Contacting an energized vehicle and ground at the same time
or approaching an energized vehicle will cause electrocution.

Verify that the outriggers are extended and
contacting the ground to provide stability before
moving booms. Plan the movements required to
move the platform and boom out of the work
area and into the stowed position without
contacting any obstructions.
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Tech Tips
Step 1

Determine what is preventing the booms from
operating.
• Is the engine running or the auxiliary pump
operating (if equipped)?
• Is the parking brake applied?
• Is the PTO operating? Can you hear the
sound of the pump?
• Check the unit/outrigger selector to verify it
is in the unit position
• Evaluate the outrigger set-up to make sure
the outriggers are deployed far enough to
close the outrigger switches (boom
interlock).
If any of the above conditions are found, remedy
the situation and retest the unit.

Step 2

Determine if the interlock solenoid is powered
for boom operation by holding a metal object
near the end of the solenoid. If metal is attracted
to the solenoid, it is energized and the interlock
is functioning properly.

Tech-Tip 73 Rev. A

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Released: 12/6/2018

Tech Tips
Step 3

If the unit solenoid valve is not energized,
manual override may be required. The unit
solenoid valve is typically located near the curb
side outrigger control valve connected to the unit
selector port. It can be identified by the manual
knob on the valve.

Solenoid

Solenoid manual override

Typical solenoid location, actual location will vary

Step 4

To override the interlock a ground person
must hold the manual override button on the
solenoid valve while the operator moves the
booms out of the work area and stores the
booms.

Tech-Tip 73 Rev. A

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Released: 12/6/2018

Tech Tips
Step 5

If the booms operated when the interlock
solenoid valve was manually operated, then
the unit must be repaired before further use.

Step 6

If the interlock system operated properly
and did not need repair, instruct the
operator(s) to follow the procedure in the
manual for proper set up before further use.
The outriggers must be extended beyond
the interlock switch location or firmly planted
to hold pressure on the outrigger cylinders.
Failure to set up the outriggers properly can
cause instability and possible overturning.
Failure to set up the outriggers properly can cause instability
and possible overturning.

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Tech Tips
Step 7

Units equipped with an optional boom
interlock that require the boom to be in the
rest to operate the outriggers will have a
similar solenoid valve with manual override.
It will be connected to the center port of the
first outrigger valve section after the
unit/outrigger selector. If the outriggers do
not operate when the boom is in the boom
rest the manual override can be used to
stow the outriggers. Repair before further
use.
Always read and follow instructions in the
unit specific manual.

Tech-Tip 73 Rev. A

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Released: 12/6/2018