Lull 944E-42 Service Manual - Manual (Page 531)

9.21 Model 644E-42/944E-42 Rev. 6/04
Electrical System
9.7 FUSES AND RELAYS
Fuses and relays help to protect the electrical system. In
general, a blown fuse is a symptom of another electrical
problem. Address the true problem, not just the symptom.
Simply replacing the fuse often will not solve the problem.
Blown fuses are usually due to simple causes, including
loose or corroded connections, or a defective relay.
There are two main causes of blown fuses; a shorted or
grounded wire in the applicable circuit, or a defective
electrical component. Visually check the condition of the
fuse, wires, connections and components in the involved
circuit before replacing a fuse. Check the circuit for
shorts, grounding, or defective electrical components.
Keep in mind that many parts in the electrical system
work with components of the hydraulic system; a careful
inspection of the related hydraulic components may help
in solving problems.
9.7.1 Circuit Protection - Fuses
a. Auto Type Fuses
The fuse is the most common method used for protecting
wiring circuits. A good fuse (1) will have the center
element connected to both sides of the fuse. Whenever
there is an excessive amount of current flowing through a
circuit the fusible element will melt (2) and create an open
or incomplete circuit.
Fuses are a one time protection device and must be
replaced each time the circuit is overloaded. To
determine if a fuse is open (2), remove the suspected
fuse and examine the element in the fuse for an open
(break). If not broken, also check for continuity using a
DMM or a continuity tester. If the element is open or
continuity is suspect, replace the fuse with one of equal
current rating.
b. Cable Type Fusible Link
(644E-42, SN 0160003690 & After Only)
There is a cable type fusible link (3) connected to the B+
terminal on the alternator and the 12V starter buss bar.
This fusible link is used for protecting the starter to
alternator circuit. A good cable will have the center fusible
link connected to both sides of the cable. Whenever there
is an excessive amount of current flowing through the
circuit, the fusible element will melt (4) and create an
open or incomplete circuit. This will not be a visible break.
To determine the status of this cable, with the ignition in
the OFF position, check for battery voltage at the
alternator connection. If there is no battery voltage the
element is open.
MT0420
1 2
Fuse Types
Current Rating Amperes Color
Auto Fuses, Mini Fuses
1
Black
2 Gray
3 Violet
5 Tan
7.5 Brown
10 Red
15 Blue
20 Yellow
25 White
30 Green
Maxi Fuses
20 Yellow
30 Light Green
40 Orange or Amber
50 Red
60
Blue
MU6640
3
4