Blog 7 min read
What to Put in a Wire Harness Pinout and Wiring Schedule
A buyer's checklist for connector views, cavity numbering, wire lists, shield notes, revision control and substitutions in a custom harness package.
Make the electrical intent unambiguous
A wire harness quote can stall when the drawing shows the product shape but not the electrical connections. A supplier needs to know which connector contacts are connected, the direction from which each connector is viewed, and how the drawing relates to the physical assembly. A clear pinout and wiring schedule reduce interpretation and revision errors.
Use the released drawing revision as the authority. Include the connector manufacturer and part number, keying or polarization, cavity count, populated and unused positions, and whether the view is from the mating face or wire side. Mark the orientation feature and provide a clear reference so the view cannot be mirrored by mistake.
Build a wire list that can be checked
For each connection, list the source connector and cavity, destination connector and cavity, wire identification, conductor specification, color or marking, and any required terminal or splice. Include circuit names or net identifiers that agree with the schematic. If a wire branches, show the branch point or define it on a controlled assembly drawing.
Keep units, abbreviations and wire-size notation consistent. State when a shield, drain wire, jumper, splice or unused cavity requires special treatment. If one circuit is intentionally open or not populated, identify it rather than leaving an empty table cell that could be mistaken for missing information.
Coordinate connector views and part numbers
Connector cavity numbering can appear different in a mating-face view and a wire-entry view. State which view is shown wherever the pinout is used. Add connector keying, locking and backshell details when they affect assembly or mating. If an approved alternate connector is allowed, document its part number and the conditions for substitution; a similar-looking housing is not automatically electrically or mechanically interchangeable.
Where terminal part numbers depend on wire size or plating, list the approved combination or identify a controlled source table. Include seals, cavity plugs, strain relief and accessories that are part of the assembly.
Control revisions and changes
The bill of materials, wiring schedule, connector view and assembly drawing should carry compatible revision identifiers. A revision table should identify what changed and when it became effective. If connector cavities, wire colors or branches change, review all documents that use the circuit definition, including test fixtures and labels.
A quotation based on a superseded drawing can produce a correct build to the wrong design. Mark obsolete files clearly and send one approved package. If a prototype deviation is accepted, record its scope, affected samples and disposition before the next build.
Use a visual harness drawing for physical routing
A pinout describes electrical connections but does not fully define the physical harness. Include a formboard or assembly view when branch locations, route, leg lengths, clips, orientation or connector exit direction matter. Dimension the relevant features from a consistent datum and define how any flexible route is measured. Do not rely on a photograph as the only controlled dimensional source.
Add labels, coverings, shield terminations and inspection points to the drawing or linked specifications. NASA-STD-8739.4 includes requirements for cable and harness interconnections and calls for methods to identify cables, connectors and wires within its scope. IPC/WHMA-A-620 is an industry consensus standard covering process and acceptance requirements for cable and harness assemblies; it does not replace a project-specific pinout or drawing.
What to send with the RFQ
Provide the schematic or netlist, connector pinout, wire schedule, assembly drawing, bill of materials and applicable specifications in a single revision-controlled package. Identify units, view orientation, approved alternates, special shield or splice treatment, and the questions still awaiting engineering decision.
State the required sample, inspection and electrical test records by reference to the approved project requirement. The supplier should not have to infer missing circuit connections from product photos or guess which file is current.
A short drawing-package checklist
1. Is every connector part number and cavity view orientation identified?
2. Does each wire row define both endpoints, conductor, color or ID, and special termination?
3. Do the pinout, schematic, bill of materials and assembly drawing share the same revision?
4. Are branches, labels, shields, unused cavities and approved alternates shown?
5. Are open questions marked and the acceptance records stated?
Frequently asked questions
Is a schematic enough to quote a wire harness?
It can define circuit intent, but a manufacturable package may also need connector views, a wire schedule, component list and physical assembly drawing. The exact package depends on the assembly and customer requirements.
Should the connector view use the mating face or wire side?
Either can be used if it is clearly labeled, oriented and consistent throughout the package. Ambiguous or mirrored views create avoidable wiring risk.
Can I send a photo instead of a drawing?
A photo can help show routing or context, but it should not replace controlled pinout, dimensions, part numbers or revision information.
What is the most important revision-control detail?
Make one approved revision the source of truth and ensure that every linked document and test definition points to it.
References
NASA and IPC describe scope for harness interconnection workmanship and acceptance. The RFQ checklist is practical documentation guidance and does not claim that a standard replaces project-specific engineering drawings.
NASA-STD-8739.4 Workmanship Standard
IPC/WHMA-A-620 Endorsement Program