Locate the cabin-mounted power distribution panel under the dashboard on the driver’s side; this is where all primary circuit protectors are grouped, and referencing its layout is the fastest way to identify faults without disassembling wiring harnesses.
Each slot in the panel corresponds to a specific circuit such as headlights, ignition, wipers, heater motor, and radio. Amperage ratings are stamped directly on the plastic housing, typically ranging from 10A to 30A. Matching these values precisely is critical–installing a higher-rated element risks overheating the wiring, while a lower rating may cause repeated interruptions under normal load.
The interior panel is complemented by an auxiliary relay and protection cluster located in the engine compartment, near the battery. This external unit manages higher нагрузочные цепи like starter control and charging system. Corrosion on contacts is common in older vehicles, so visual inspection and cleaning with contact spray often restores functionality without component replacement.
Color-coded wiring simplifies tracing: orange usually indicates constant power, pink relates to ignition-switched circuits, and black serves as ground. Use a multimeter to confirm voltage presence before replacing any component, as failures are frequently caused by degraded connectors rather than the protective elements themselves.
1987 GMC Sierra Fuse Box Diagram
Locate the electrical panel under the dashboard on the driver’s side and match each circuit to its slot using factory labeling stamped on the cover; for quick troubleshooting, check the following positions and ratings that commonly fail under load:
- Headlamps circuit – 20A, left column, upper section
- Turn signals and hazard lights – 15A, central row
- Wipers and washer pump – 25A, right column
- Heater and blower motor – 30A, lower right corner
- Radio and interior lighting – 10A, mid-left section
Use a test light or multimeter to verify continuity before replacing any element; corrosion on контакts often mimics a blown insert, so clean terminals with contact cleaner and recheck voltage at both sides of each slot. If multiple systems fail simultaneously, inspect the bulkhead connector and grounding points near the kick panel rather than swapping parts blindly. For modified trucks with added accessories, confirm that auxiliary wiring is not tapped into low-amperage circuits, as this leads to repeated overload and melted plastic around the panel.
Exact Location of Interior and Engine Bay Fuse Boxes in 1987 GMC Sierra
Check under the driver-side dashboard first: the interior electrical panel sits slightly left of the steering column, mounted against the lower firewall. Access requires crouching near the pedals and looking upward; a small rectangular cover, often secured by clips, conceals the circuits. Removing this panel exposes labeled slots aligned in horizontal rows.
The cabin unit is positioned close to the parking brake assembly, which helps identify it quickly without dismantling surrounding trim. In some trims, a thin plastic shield or knee bolster partially blocks access, so loosening two to four screws may be necessary. Lighting is limited in this area, so using a handheld lamp prevents misidentification of terminals.
Under-hood placement is different and easier to reach. The engine compartment distribution center is mounted along the driver-side fender well, typically near the battery tray. It appears as a black rectangular housing with a removable lid, often marked with molded text indicating circuit protection components.
Lift the cover by releasing side tabs; inside, you’ll find larger protection elements and relays arranged in a grid. This compartment handles high-load systems such as headlights, charging circuits, and ignition-related components. Corrosion or dirt accumulation is common here due to exposure, so inspect contacts closely.
Some variants place an auxiliary inline holder near the firewall on the passenger side. This smaller unit protects specific accessories like HVAC or aftermarket additions. It may be attached to wiring harnesses rather than mounted to metal, so tracing wires from the main loom can help locate it.
For precise identification, match wire colors and connector shapes rather than relying on cover markings alone. Over decades, replacements and modifications may alter original layouts, so visual verification of each slot’s function is more reliable than assumptions based on position.