There is no price list for a custom harness, because six variables decide it — and three of them are set by the buyer, not the supplier.
A custom harness has no unit price until six variables are fixed, which is why a supplier who quotes one from an email is giving you a placeholder rather than a price. The useful answer to "how much does it cost" is not a number — it is the list of what moves the number, and which of those things you are still free to change.
Two harnesses with the same circuit count, the same length and the same connector count can differ by a factor of three on unit cost. The difference is not margin and it is not supplier efficiency — it is that one of them is a straight run with a few branches and the other is a tightly dressed assembly with sleeving, sealed connectors and a test requirement on every circuit. A quote produced before those questions are answered is a quote for the average of two very different parts.
| # | Factor | What moves it | Whose choice |
|---|---|---|---|
| 1 | Wire | Gauge, insulation material and total cut length. Silicone costs several times PVC and is chosen for temperature, not for preference. Length is counted per circuit, including the waste on the long ones. | Buyer, via the specification |
| 2 | Terminals and connectors | Branded automotive-grade housings, terminals and seals against catalogue equivalents. Plating matters: tinned and gold-plated terminals differ both in price and in the corrosion cases they survive. | Buyer, via the BOM |
| 3 | Labour | Circuit count, branch count, and how much handling the part needs. Sleeving, conduit, tape wrap direction and a tight bend radius all add operator minutes per set. | Shared |
| 4 | Tooling and fixtures | A forming board, a test fixture or a sealing mould is a one-off cost that has to be recovered. Amortised over 500 sets it dominates; over 50,000 sets it is noise. | Shared, decided by volume |
| 5 | Test requirement | Continuity only, or continuity with a hipot and resistance limits. Sealed parts add a leak test; shielded parts add a shield-continuity measurement. | Buyer, via the drawing notes |
| 6 | Volume and its stability | Annual quantity, whether it is firm or forecast, and whether the mix is stable enough to run the part on an automatic machine or only on a semi-automatic one. | Buyer |
Three of the six are set by the specification, which means they are yours to decide before the enquiry goes out — and they are where a programme gets expensive after the award rather than before it.
The cost that does not appear on the quotation is the cost of the escape. On a harness, a single missed crimp in an assembled vehicle is not a credit note — it is a line stoppage, a warranty claim or a recall investigation. Those costs land on the buyer even when the supplier pays for the parts, because the buyer owns the consequence.
That is the argument for reading a quote as a specification document rather than a number. Four questions to a quote, before comparing totals:
Where the answers differ, the totals are not comparable and the cheaper one has not won anything.
The simplest way to get comparable numbers is to ask every supplier for the same break-down, and to ask for it as part of the RFQ rather than after the fact. Five lines are enough: wire and insulation, terminals and connectors, labour, tooling or fixture amortisation, and test. A supplier who returns a single unit price and refuses to break it down has either not costed it or does not want you to see the structure — both are reasons to keep looking.
The weighting of the six factors changes with the family you are buying:
Only as a range, and it will be wide enough to be of limited use — which is why the honest answer is to send whatever you have instead. A drawing, a sample, or a written description of the circuit count, the connector types and the environment is enough to quote from. If you genuinely have nothing but a target cost, send the target and the annual volume; a supplier can then tell you which of the six factors has to move to reach it, which is more useful than a price that turns out to be unreachable at the first drawing revision.
It depends on the part rather than on a policy number, which is why ours is quoted per project. The real driver is tooling: an assembly that needs a forming board, a test fixture or a sealing mould has a one-off cost that has to be spread over the order, so a low first order is possible but the amortisation shows up in the unit price. A part that can be built on a semi-automatic line from standard terminals has much less of a floor. If your requirement is genuinely small, say so up front and ask for the tooling cost as a separate line — that is the number that decides whether a small first order makes sense.
Almost never because of margin. The usual causes are different assumptions about the terminal brand, a sample priced as though it were production, a test scope that differs between quotes, or the awkward minority of circuits quoted at the same rate as the easy majority. None of those are visible on a quotation form, which is why asking for a five-line break-down is worth more than asking for a best price. If two quotes differ by 40% and the break-downs match line for line, then something about the specification is genuinely ambiguous and the drawing needs fixing before the award, not after.
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