Isuzu N-Series. Manual — part 1075
8-12 CAB AND CHASSIS ELECTRICAL
Wire Size Table
Fuse, Fusible Link and Circuit Breaker
Fuse
Fuses are the most common form of circuit protection
used in vehicle wiring. A fuse is a thin piece of wire or
strip of metal encases in a glass or plastic housing. It is
wired in series with the circuit it protects. When there is
an overload of current in a circuit, such as a short of a
ground, the wire or metal strip is designed to burn out
and interrupt the flow of current. This prevents a surge
of high current from reaching and damaging other com-
ponents in the circuit.
Determine the cause of the overloaded before replacing
the fuse.
The replacement fuse must have the same amperage
specifications as the original fuse.
Never replace a blown fuse with a fuse of a different am-
perage specification.
Doing so can result in an electrical fire or other serious
circuit damage. A blown fuse is easily identified.
N8A0025E
Nominal size
Cross sectional area
(mm
2
)
Outside diameter
(mm)
Allowable current
(A)
AWG size
(cross reference)
0.3
0.5
0.85
1.25
2
3
5
8
15
20
0.372
0.563
0.885
1.287
2.091
3.296
5.227
7.952
13.36
20.61
1.8
2.0
2.2
2.5
2.9
3.6
4.4
5.5
7.0
8.2
9
12
16
21
28
37.5
53
67
75
97
22
20
18
16
14
12
10
8
6
4
N8A0026E
CAB AND CHASSIS ELECTRICAL 8-13
Fusible Link
The fusible link is primarily used to protect circuits where
high amounts of current flow and where is would not be
practical to use a fuse. For example, the starter circuit.
When a current overload occurs, the fusible link melts
open and interrupts the flow of current so as to prevent
the rest of the wiring harness from burning.
Determine the cause of the overload before replacing
the fusible link. The replacement fusible link must have
the same amperage specification as the original fusible
link.
Never replace a blown fusible link with fusible link of a
different amperage specification. Doing so can result in
an electrical fire or other serious circuit damage.
A blown fusible link is easily identified.
Fusible Link Specifications
Circuit Breaker
The circuit breaker is a protective device designed to
open the circuit when a current load is in excess of rated
breaker capacity. If there is a short or other type of over-
load condition in the circuit, the excessive current will
open the circuit between the circuit breaker terminals.
The reset knob pops out when the circuit is open. Push
the reset knob in place to restore the circuit after repair-
ing it.
Relay
Battery and load location may require that a switch be
placed some distance from either component. This
means a longer wire and a higher voltage drop 1.
The installation of a relay between the battery and the
load reduces the voltage drop 2.
Because the switch controls the relay, amperage
through the switch can be reduced.
N8A0027E
Type
Rating
Case Color
Maximum Circuit Current (A)
Connector
30 A
Pink
15
Connector
40 A
Green
20
Bolted
50 A
Red
25
Bolted
60 A
Yellow
30
Bolted
80 A
Black
40
N8A0028E
N8A5028E
8-14 CAB AND CHASSIS ELECTRICAL
Relay Specification, Configuration and Inspection
Name/
Color
Rated voltage/
Coil resistance
Internal circuit
Name/
Color
Rated voltage/
Coil resistance
Internal circuit
MR5C
(1T)/
Black
12 V/
Approx. 90
Ω
Minimum
operating
voltage: 7 V
at 25
°C (77°F)
MR82C/
White
label
12 V/
Approx. 23
Ω
Minimum
operating
voltage: 7 V
at 20
°C (68°F)
MR5C
(1T)/
Brown
12 V/
Approx. 90
Ω
Minimum
operating
voltage: 10.5 V
at 25
°C (77°F)
MR5C
(1T)/
Green
24 V/
Approx. 266
Ω
Minimum
operating
voltage: 16 V
at 25
°C (77°F)
MR82C/
Green
label
24 V/
Approx. 100
Ω
Minimum
operating
voltage: 16 V
at 20
°C (68°F)
MR5C
(1T)/
Grey
24 V/
Approx. 266
Ω
Minimum
operating
voltage: 20 V
at 25
°C (77°F)
(connector face)
(connector face)
Inspec-
tion
The
way
Check to see if
there is any conti-
nuity between the
relay terminals.
Inspec-
tion
The
way
Check to see if
there is any conti-
nuity between the
relay terminals.
Result
(When no voltage is
applied relay terminals 2
-4)
3 -5
→ continuity
1 -5
→ No continuity
Inspection
Result
(When no voltage is
applied relay terminals 4
-5)
2 -3
→ No continuity
Normal
Normal
Abnormal
(When minimum operat-
ing voltage is applied
relay terminals between
2 -4)
3 -5
→ continuity
1 -5
→ No continuity
Abnormal
(When minimum operat-
ing voltage is applied
relay terminals between
4 -5)
2 -3
→ No continuity
Normal
(When minimum operat-
ing voltage is applied
relay terminals between
2 -4)
3 -5
→ No continuity
1 -5
→ continuity
Normal
(When minimum operat-
ing voltage is applied
relay terminals between
4 -5)
2 -3
→ continuity
N8A0431E
N8A0433E
1
3
5
1
3
5
4
2
N8A0432E
N8A0434E
CAB AND CHASSIS ELECTRICAL 8-15
Name/
Color
Rated voltage/
Coil resistance
Internal circuit
ACM
13221
M04/
Black
12 V/
Approx. 120
Ω
Minimum
operating
voltage: 8 V
at 25
°C (77°F)
ACM
13222
M01/
Green
24 V/
Approx. 320
Ω
Minimum
operating
voltage: 18 V
at 25
°C (77°F)
(connector face)
Inspec-
tion
The
way
Check to see if
there is any conti-
nuity between the
relay terminals.
Result
(When no voltage is
applied relay terminals 3
- 5)
1 - 4
→ continuity
1 - 2
→ No continuity
Inspection
Normal
Abnormal
(When minimum operat-
ing voltage is applied
relay terminals between
3 - 5)
1 - 4
→ continuity
1 - 2
→ No continuity
Normal
(When minimum operat-
ing voltage is applied
relay terminals between
3 - 5)
1 - 4
→ No continuity
1 - 2
→ continuity
N8A5571E
N8A5572E
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