What Goes Into Reverse Engineering an Electrical Harness

Reverse engineering a harness isn’t just measuring wires—it’s a detailed engineering process designed to rebuild accurate, production-ready documentation from an existing physical harness. Here’s what’s involved:

1. Discovery & Intake

• Review the customer’s goals (new vendor sourcing, redesign, standardization, documentation cleanup, etc.)

• Identify available data: old schematics, drawings, BOMs, wiring lists, or nothing at all.

• Determine configuration variants.

2. Physical Harness Inspection

• Carefully unwrap and evaluate the physical harness.

• Document all protective coverings, branch points, and overmolds.

• Identify connectors, terminals, seals, boots, and any special components.

3. Wire-by-Wire Mapping

• Trace every circuit end-to-end—no assumptions.

• Record wire colors, gauges, strip lengths, and any printing/legends.

• Note splices, junctions, breakout points, grounding paths, and routing logic.

4. Connector & Component Identification

• Identify connector part numbers (OEM, TE, Molex, Deutsch, Aptiv, etc.).

• Verify keyed positions, cavity plugs, seals, wedges, terminal types, locking features.

• Document mating components when present.

5. Detailed Measurement

• Overall harness length

• Branch lengths and splits

• Breakout angles

• Protective coverings (loom, braid, conduit, heat shrink)

• Clamp points and strain relief features

This becomes the foundation for a production-ready drawing.

6. Electrical Documentation Build-Out

A. Electrical Schematic

• Every circuit redrawn clearly and accurately

• Source → load paths validated

• Fuse/relay sizing verified

• Wire lengths updated for voltage drop if required

B. Production-Ready Harness Drawing

• Full 2D harness layout with dimensions

• Connector callouts

• Wire lists

• Splice tables

• Bill of materials

• Manufacturing instructions

C. 3D Model & Routing (optional but highly valuable)

• Full 3D routing into the equipment model

• Envelope and clamp locations defined

• Interference checks performed

• Length optimization for production efficiency

7. Validation & Quality Checks

• Cross-check every connection

• Match schematic to harness drawing wire-for-wire

• Confirm BOM accuracy

• Validate manufacturability and serviceability

8. Optional Engineering Improvements

During reverse engineering, it’s common to identify:

• Overlength or underlength wire runs

• Missing documentation

• Common failure points

• Opportunities for routing cleanup

• Splice or connector count reduction

• Better serviceability options

These improvements can reduce warranty issues and production time.

9. Deliverables to the Customer

CPE typically provides:

• Accurate, clean schematic

• Full production-ready harness drawing set

• BOM with sourceable components

• Optional 3D routed harness model

• Revision history and notes