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