Cable harness pricing is unusually sensitive to design details. The same electrical function can cost 2–3x more depending on connector series, wire callouts, and how the drawing is documented. Most of these choices are trivial to change before the design freezes and painful to change after.
Here are 12 DFM fixes we flag on almost every harness RFQ.
1. Use standard connectors
TE, Molex, JST, Amphenol, Deutsch, Souriau — stick with high-volume series in each. Exotic MIL-spec circular connectors (D38999, MIL-DTL-26482) are correct for aerospace but often overkill for industrial or commercial.
Rule of thumb: if you cannot find the connector at two US distributors with stock, expect long lead times and price premiums.
2. Match contact size to wire gauge
Every contact has a wire-range spec. Using a 20 AWG contact for a 24 AWG wire is a crimp failure waiting to happen — and every reputable harness house will refuse to build it. Cross-check contact PN against wire gauge on the BOM.
3. Do not over-spec wire gauge
An engineer worried about voltage drop will spec 18 AWG "just to be safe." A 22 AWG wire is often perfectly adequate, cheaper, more flexible, and easier to route. Do the ampacity math against the actual current and length.
4. Do not under-spec insulation temp
Automotive under-hood and near motors sees 105–150 °C. General PVC insulation is rated 80 °C. Under-speccing insulation is a warranty problem later.
5. Consolidate wire types
A harness with 6 different wire specs (color, gauge, insulation) costs more to build than one with 3, because setup and part counts multiply. Consolidate where you can.
6. Give branches real tolerances
"Approximately 300 mm" is not a spec. Every branch length needs a nominal and a tolerance (typically ±10 mm or ±25 mm depending on function). Without tolerances, the builder guesses, and the guesses will not match yours.
7. Call out breakout points, not just endpoints
A harness drawing that only dimensions endpoints leaves the builder to guess where branches split. Dimension each breakout from a reference end.
8. Use standard heat shrink
Standard 2:1 or 3:1 polyolefin shrink in black is a stock item. Custom colored, printed, or 4:1 shrink is a special order. Use standard unless you have a reason.
9. Label with printed shrink, not tape
Printed heat shrink labels are permanent, cheap in volume, and easy to inspect. Wrap-around tape labels fall off in the field. Spec printed shrink at every ID location.
10. Group circuits into overbraids only when needed
Expandable braided sleeving (Techflex) adds cost. Use it where abrasion or bundle appearance matters. Don't wrap every branch by default.
11. Specify a build class
Call out IPC/WHMA-A-620 class (1, 2, or 3) on the drawing. Without a class, builders default to Class 2, which is usually correct — but if you need Class 3 for aerospace or medical, say so up front so the quote reflects it.
12. Include test requirements
Continuity and hipot testing are standard. If you need insulation resistance, dielectric withstand at a specific voltage, or functional test on the assembly, call it out. Every test adds cost — but adding it after the fact costs more.
The RFQ package that gets a fast quote
- Wiring diagram or pinout table.
- Cable drawing with dimensioned branches.
- BOM (wire, connector housings, contacts, seals, backshells, sleeving, labels).
- Test spec.
- IPC/WHMA-A-620 class.
- Volume and target ship date.
Send it and you will get a firm number in a few days. Start your harness RFQ here.