The harness print checklist.

Harness print checklist

A print that covers these ten items gets priced the first time with no back-and-forth. If yours is missing some, send it anyway. The redline lists every assumption.

1. Wire gauge and type on every circuit. Call out the gauge and the insulation type, such as 16 AWG GXL. "16 AWG" alone leaves the wire type open, and GXL, TXL and SXL differ in wall thickness, heat rating and price.
2. Lengths with tolerances. Give each branch length from a clear datum and a tolerance, such as ±13 mm. Without tolerances every supplier guesses differently, and the parts may not fit your routing.
3. Connector, terminal and seal part numbers. List the full stack for each cavity: housing, terminal, seal and secondary lock. The housing number alone is not enough to price or build the part.
4. Pinout for every cavity. Show which circuit lands in which cavity, including unused cavities and the plugs that fill them. An open cavity in a sealed connector lets water in.
5. Wire colors or circuit IDs. Colors or printed circuit IDs let the harness match your schematic and make service work faster.
6. Label and marking format. Say what each label reads, what it is made of and where it sits. Part number, rev and date code is a good default.
7. Covering for each branch. Split loom, braid, tape or heat-shrink, and where each one starts and stops. Covering drives both cost and abrasion life.
8. Rev letter and date in the title block. A clear rev and date keeps samples, production and service parts in step when the drawing changes.
9. Test requirements. State what has to pass: continuity, hi-pot, pull test values. If nothing is stated, we quote a 100% continuity test.
10. Annual usage and release size. How many a year and how many at a time. Volume sets the price, and release size sets how stock is held.

Six failure points to design out

1. Chafe at pass-throughs

Vibration wears insulation through wherever the harness crosses a frame rail or sheet-metal edge. Call out a grommet or abrasion sleeve at every pass-through.

2. Crimp quality

Under-crimped terminals pull out, and over-crimped ones crack later. Crimp height should be checked at every setup and confirmed with cross-sections.

3. Missing secondary locks

A connector that never fully latched works loose in service. Specify the secondary lock and check it at final test.

4. Fretting on mated pairs

Micro-movement under vibration wears contact plating until the circuit drops out. Match the connector family and plating to the vibration it will see.

5. Unplugged cavities

An empty cavity in a sealed connector lets water in. Add cavity plugs to the BOM.

6. Tight bends at connector exits

Strands break inside the insulation where nobody can see them. Set bend radius and strain relief to how the harness actually mounts.

Glossary

GXL / TXL / SXL

SAE J1128 cross-linked automotive primary wire. TXL has the thinnest wall and SXL the thickest.

Crimp height

The measured height of a crimped terminal barrel, checked against the terminal maker's spec.

Pull test

A test that pulls the wire out of a crimped terminal to confirm the crimp holds at least its rated force.

Cross-section

A cut-and-polished view through a crimp that shows strand compaction and any voids.

Hi-pot

A high-voltage test that checks insulation between circuits.

AQL

Acceptance quality limit: the sampling plan used to inspect a lot before it is released.

PPAP

Production part approval process: the document package that approves a part for production.

Release program

Finished stock held for your part and called off in lots as you need it, also known as kanban or VMI.