Description

Atlas Copco ST3.5 Wiring Diagram – Factory Electrical Schematics for Underground Loaders

I’ve seen more fried ECUs from guys chasing grounds with a test light than I care to count. If you’re working on an Atlas Copco ST3.5, you need the factory Wiring Diagram—not a third-party redraw that missed a pinout. This is the actual OEM document, 36 pages of drawings that came off the line in Sweden. Every hydraulic line, every wire harness, every component box junction is mapped the way Atlas Copco built it. You don’t guess on an underground loader. You follow the schematic that the engineers signed off on.

36 Pages of Factory Electrical and Hydraulic Drawings

This isn’t a service manual. It’s a dedicated diagram and drawing set covering six system drawings and two full sections on electrical schematics and harness layouts. Page 2 gives you the steering system flow with pump displacement and priority flow divider values. Page 6 lays out the brake system including remote bleeders—critical when you’re bleeding a bogie axle 200 feet underground. The electrical section starts with the full machine electrical system, then breaks down the component box, instrument panel, and reverse alarm circuit. You get the wire colors, connector pins, and ground points. No condensed cheat sheets.

What Systems Are Covered in This Wiring Diagram?

Every major system on the ST3.5 is drawn out: steering, dump & hoist, Brake, transmission & converter, transmission shift control, swivel hinge, lubrication, Fuel, hydraulic throttle, and fire suppression. That’s ten hydraulic circuits in the system drawings section alone. Then the Electrical drawings run through the component box, instrument panel, and reverse alarm. The harness section lists C1–C4, C2-Engine, C3–C5, Comp.box-Engine, C6, and front lights. If you’re swapping a Transmission or chasing a no-start, the wiring is right there.

Brake System: Remote Bleeders and Pressure Diagnostics

The brake system drawing (page 6 in the TOC) includes the remote brake bleeders and the secondary brake valve pilot line. If you’ve ever had a brake drag because a bleeder was half-shut or a check valve stuck, you know how much time a clear schematic saves. The Atlas Copco hydraulic throttle system is also shown with pilot ports and relief valve settings. You won’t find these details in a generic “electrical manual.” This is the real deal.

Get the Right Harness Layouts for Engine and Component Box

Harness routing matters. The C2-Engine harness shows exactly where the wires break out for the injection pump, sensors, and starter. The component box harness (Comp.box-Engine) ties the ECM to the machine interface. If you’re installing a rebuilt engine or converting a ST3.5 to a different controller, these drawings are your template. Without them, you’re pinning wires by continuity alone—slow and risky. Related manuals: Atlas Copco ROCKET BOOMER M2D Diagrams, Atlas Copco ROCKET BOOMER Wiring Diagram, Atlas Copco Boomer S1D Diagrams and Drawings.

3 Reasons to Use OEM-Only Documentation for Underground Equipment

First, aftermarket wiring diagrams often omit the hydraulic interlock circuits—like the pilot line from the steering valve that disables the dump control when the brake is engaged. This Atlas Copco drawing shows those interlocks. Second, harness part numbers are listed on each drawing; you can order the correct replacement based on the sheet issue. Third, the format is scan-friendly PDF with bookmarks at every section. No flipping through 200 pages of text to find a fuse. For outside context, check Automotive Wiring basics or Automotive Industry Overview to understand why OEM standards matter.

Does this manual cover the fuel system?

Yes, the fuel system drawing is listed under System Drawings (page 6).

How does this factory diagram differ from a generic electrical schematic?

A generic schematic gives you a theoretical circuit with no machine-specific pin numbers, wire colors, or harness routing. This Atlas Copco ST3.5 Wiring Diagram shows exact connector views (e.g., C1–C4 harness), component locations in the instrument panel, and cross-references between hydraulic and electrical systems. The brake system drawing includes the remote bleeders and secondary brake valve pilot line—details you won’t find in any third-party document. It also includes the document note referencing instruction manual 5580 0012 00, which must be followed during service. That level of traceability is what keeps a loader from rolling away on a slope.

You’re not going to trace a short in a ST3.5 with a photocopy of a photocopy. This is the original factory PDF that Atlas Copco released for the Scooptram. Every wire, every hose, every valve port is where it’s supposed to be. Access the Factory Manual and keep it on your tablet next to the hydraulic test kit. That’s how you finish a shift without a tow.