Harness Routing Guidelines (DFM)
Ensuring survivability through proper physical design.
A perfectly crimped terminal is useless if the harness routing rips the wire out of the connector during chassis flex. Proper 3D routing design is the first line of defense against warranty claims.
1. Minimum Bend Radii
Forcing a wire to bend too sharply strains the insulation and can cause the copper strands on the outside radius to yield, while buckling the strands on the inside radius.
- Standard Primary Wire: The general rule of thumb is a minimum bend radius of 3x to 5x the outer diameter (OD) of the wire bundle.
- Coaxial / HSD Cables: These are highly sensitive to crushing, which changes the dielectric distance and ruins impedance. The minimum bend radius is typically strictly enforced at 10x OD.
- High Voltage Cables: Due to thick insulation and stiff shielding, EV cables require large sweeping bends (often 6x to 8x OD depending on flexibility class).
2. Drip Loops
Water follows gravity and surface tension. If a harness is routed downward directly into a connector on a sensor, condensation or splashed water will travel down the harness and pool at the back of the connector seal.
Always route the harness to dip below the connector before rising up to mate with it. This creates a "drip loop," forcing water to collect at the lowest point of the wire and drip off, rather than pressing against the connector seals.
3. Strain Relief and Tie-Down Points
A connector should never bear the physical weight of the harness bundle, nor should it act as the primary retention point against vibration.
- A mounting clip, zip-tie, or channel guide should be placed within 100mm to 150mm of the connector body.
- Ensure the wire bundle approaches the connector perfectly straight; applying an off-axis pull load causes terminal fretting and defeats the peripheral seal.
4. Clearance to Heat Sources
Radiant heat can destroy insulation even if the wire never touches the hot component. Maintain strict clearances (typically >100mm depending on the heat shield configuration) from exhaust manifolds and catalytic converters. If routing is constrained, employ localized reflective shielding (e.g., aluminized fiberglass sleeving) over the affected harness segment.