How to Specify Wire Harness Lengths and Tolerances

Start With Two Length Definitions

A drawing can become confusing when one length describes two different things. State whether each dimension refers to cut wire length or finished assembly length. Cut wire length describes the conductor before terminals, seals, backshells, sleeving or other assembly features change its installed position. Finished assembly length describes the completed harness between defined reference points.

Put the applicable length definition beside each critical dimension. Identify whether it is for a straight preparation step or the completed part as installed. If both values matter, show both and explain their relationship.

Put Measurement Endpoints on the Drawing

Do not rely on a label such as overall length without showing the endpoints. Define the measurement from a connector face, connector exit, terminal hole center, backshell reference or another clearly identified datum. These are drawing examples, not universal rules: choose the endpoint that matches how the assembly locates and fits in your equipment.

Add a detail view when the endpoint could be read in more than one way. Mark the reference on the connector outline, terminal view or assembly silhouette, use the same convention throughout, and state the measurement condition when it matters.

Control Branch Datums and Orientation

Branch length is useful only when its origin is repeatable. Identify the branch datum and dimension direction. A datum might be the centerline of a breakout, sleeve edge or another physical feature. Name it on the drawing rather than leaving the origin to a work instruction or email.

Use a connector face view, keyway direction, clocking mark or orientation note so length and branch positions are understood relative to the installed part. If a connector can rotate, say whether orientation is fixed, keyed, or confirmed during sample fitting.

Set Tolerances From Fit Requirements

A tolerance should describe what the equipment can accept, not fill an empty box with a familiar plus-or-minus value. Review the clearance, mating reach, strain-relief position, service loop, adjacent components and installation sequence. Then set the actual tolerance for each important dimension based on the fit and function of that location.

Separate critical dimensions from reference dimensions. A connector-to-connector location, branch breakout or mounting feature may need a controlled limit, while a non-locating free leg may be governed differently. Make the acceptance condition explicit: the harness must mate without forced loading, reach the mounting point, and leave the intended service movement. Record the agreed measurement method alongside the dimension so supplier inspection and installation checks use the same reference.

Account for Routing and Flex

A finished harness may need extra material to follow its route, move with a mechanism or avoid transferring force into a connector. Show the routing path, tie points, clips, support locations, service allowance and flex or movement requirements. If it passes through a constrained opening, include the installation sequence.

Routing allowance and bend behavior must follow the specifications of the selected wire, connector, terminal, backshell and protective component manufacturers. Do not copy a universal bend-radius rule into the drawing. Confirm the relevant product documentation for the exact component combination, especially where a connector application specification warns against excessively sharp bending.

Close the Loop With Revision and Sample Approval

Before release, check that every length has a defined endpoint, every branch has a datum, connector orientation is unambiguous, and the drawing distinguishes cut length from finished length. Record the drawing revision, part references, open assumptions, requested quantity and the agreed inspection or measurement condition.

For a new or changed harness, approve a sample for physical fit before treating the drawing as settled. Check mating, routing, branch locations, strain relief, clearance, movement and installation sequence. Record any adjustment against a revision-controlled drawing, and confirm which changes require a new sample.

When you are ready to review a wire harness drawing or sample, send the available information through the HPC contact page so the project can be discussed against the actual assembly and application.

References

The references support project-specific drawing and connector-application guidance. They do not establish universal tolerance values or a universal measurement method for every harness.

TE Connectivity product drawing guidance for 2405416-1

TE Connectivity SGI 1.25 and 1.5 connectors application specification

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