This detailed document provides the essential Fuse and Relay Diagram and layout information for these earlier generation trucks. Unlike modern trucks with complex multiplex systems, the 1985–2000 models rely on simpler, robust wiring protected by clearly defined fuse and relay banks. However, decades of use, corrosion, and previous repairs make accurate diagrams absolutely vital for effective troubleshooting.
What the 1985-2000 F-Series Manual Covers:
This guide offers clear, visual documentation for all primary power distribution points on your classic Isuzu Forward truck:
-
Fuse Panel Locations: Clear identification of the main fuse box locations, typically found in the cab interior (under the dash or side panel) and sometimes in the engine compartment.
-
Circuit Identification: Detailed diagrams showing the number, amperage (rating), and primary function (e.g., "Ignition," "Headlamps," "Wipers") of every circuit fuse.
-
Relay Functions: Clear labeling and diagrams identifying the function of key relays for high-draw systems like the Starter, Horn, Headlights, and Blower Motor.
-
Engine Specifics: Coverage for the common engine configurations of this era, including the reliable 6BG1 and 6HE1 diesel engines, focusing on their ignition and glow plug circuits.
-
Corrosion Aid: This documentation is perfect for tracing circuits where corrosion or previous repairs have led to unreliable connections or unmarked fuses.
Engine: 6BG1, 6HE1, 6HH1, 6SA1
Location of Relays and Fuses
The fuse block (1) is located behind the instrument panel. To access the fuse block, lower the cover (2). Information regarding fuse ratings and the protected circuits is contained on the reverse side of the cover (see diagram "Fuse Block").
| No. | A (Amperage) | Function Description (English) |
| 1 | 20A | HEADLAMP MAIN |
| 2 | 15A | HEADLAMP UPPER RH |
| 3 | 15A | HEADLAMP UPPER LH |
| 4 | 15A | HEADLAMP LOWER RH |
| 5 | 15A | HEADLAMP LOWER LH |
| 6 | 15A | AUDIO SYS. CIGAR LIGHTER |
| 7 | 15A | METER WARN. LPS. ACG(L) |
| 8 | 15A | EXH BRK. BACK-UP LPS |
| 9 | 15A | AIR DRYER. DRAIN HEATER |
| 10 | 15A | ID & CLEAR LPS |
| 11 | 20A | TAIL. LICENSE PLATE & OTHER ILLUMINATION |
| 12 | 20A | WIPER & WASHER ENG STOP |
| 13 | 20A | STOP LPS. HORN |
| 14 | 20A | TURN SIG & HAZZARD WARN DOME LIGHT |
| 15 | 20A | AIRCON SYS (COOL COND FAN) |
| 16 | 15A | GLOW RELAY |
| 17 | 15A | STARTER (C) |
| 18 | 20A | AIRCON SYS (M/CL COMP) |
| 19 | 15A | AIRCON SYS (COOL COND FAN) |
| 20 | 15A | AIRCON SYS (COOL COND FAN) |
18,19,20 Fan motor relay
Relay Block (modifications FVR, FSR, EVR)
The Relay Block is located on the left under the instrument panel.
1 - electromagnetic clutch relay PTO (modifications FVR, FSR)
2 - horn relay (modifications FVR, FSR)
3 - parking brake relay (modification EVR)
4 - candle preheating relay
5 - stop signal relay
6 - relay retarder
7,8 - spare relay
9 - turn signal flasher relay
10 - windshield wiper relay
11 - relay room blower
12 - electromagnetic clutch relay air conditioner compressor
13 - rear fog light relay
Relay block (modification FTR):
1 - ventilator fan motor relay
2 - horn relay
3 - turn signal flasher relay
4 - windshield wiper heater relay
5 - candle preheating relay
6 - sound signal relay
Write a comment