Substance Declarations for Imported Wire Harnesses: What to Demand, Per Part

The email that starts most of these problems is short and reassuring. You ask a harness supplier for substance documentation and back comes a single PDF on company letterhead: We hereby declare that all products supplied by our company comply with international environmental requirements. It is signed, it is stamped, and it is worth nothing. It names no part number, no substance, no test method, no laboratory and no date of the list it claims conformity against. If a market-surveillance authority in Germany or a customer's compliance team in Ohio asks you to substantiate a claim about the assembly in your product, that letter is not evidence — and the obligation is yours, not your supplier's. This is what a usable substance declaration for an imported wire harness looks like, why it has to be issued per part number, and how to read the test report that is supposed to sit behind it.

Who actually carries the obligation

Start with the uncomfortable part. Under the EU regime for electrical and electronic equipment, when you bring product in from outside the union you take on the importer's duties: you must be able to show that the equipment you place on the market meets the restricted-substances requirements, and you must hold technical documentation to that effect for a decade after the last unit is placed. Your Shenzhen supplier is not the entity a national authority will contact. You are.

The two EU instruments that reach a wire harness are different in kind and are frequently confused:

• Directive 2011/65/EU, as amended (notably by Directive (EU) 2015/863, which took the restricted list to ten substances by adding four phthalates), restricts specified substances in electrical and electronic equipment. It reaches your harness because the harness is a part of finished equipment. The limits are concentration limits by weight in each homogeneous material — generally 0.1%, with cadmium at 0.01%.
• Regulation (EC) No 1907/2006 creates a communication duty: where an article contains a candidate-list substance of very high concern above 0.1% by weight, the supplier must pass information down the chain (Article 33), and suppliers placing such articles on the EU market have a separate database notification duty under the waste framework legislation, Directive 2008/98/EC.

Confirm the current numbering and any amendment in force before you paste these into a contract; the substance annexes and the exemption lists move on their own schedules.

The documentation standard that ties it together on the EU side is EN IEC 63000, which describes the technical file an importer assembles from supplier declarations, materials data, test reports and analysis. That is the point buyers miss: the file is built from component-level evidence. If your evidence is one letter covering "all products", you do not have a file, you have a sentence.

For the US side, the equivalent pressure is state-level rather than federal. California's Proposition 65 is the reason so many cords and cables carry a warning label — lead in brass and certain phthalates in flexible PVC are exactly the chemistries a harness is built from. If any of your volume ships to California, decide the labelling question at specification time, not when a demand letter arrives.

A harness is not one material — and that is the whole problem

The restricted-substance limits apply per homogeneous material: a material that cannot be mechanically disjointed into different materials. A finished harness is a stack of them. Count the ones in a perfectly ordinary multi-branch loom:

Twenty-plus homogeneous materials is normal. A declaration that treats "the harness" as one item cannot possibly be a statement about any of them.

The brass terminal detail that catches people out

Here is the check that separates buyers who have done this from buyers who have not. Copper alloys used for terminals frequently contain lead deliberately, for machinability — and the restricted-substances regime accommodates this through an exemption for lead as an alloying element in copper up to a stated percentage by weight. Exemptions are numbered, they have expiry dates, and they get renewed, narrowed or allowed to lapse on their own cycle.

So when a supplier sends you a terminal declaration that reports lead as not detected, you have learned something — usually that the laboratory tested the plating, or that the declaration was copied from a template. The technically correct document for a leaded brass terminal states the lead content and names the exemption it relies on, with the exemption number. A declaration that claims a cleaner result than the metallurgy allows is a bigger warning sign than an honest one that invokes an exemption.

Ask, in writing: for each metal part, does the declaration rely on an exemption, and if so which numbered exemption and what is its expiry? That question alone tells you whether anyone at the supplier has read the documents they are forwarding.

Reading the test report behind the declaration

A declaration is a claim. The report is the evidence, and reports vary enormously in what they actually cover.

Check the method, not the logo. Analytical methods for these substances are described in the IEC 62321 series — different parts for different analytes, including screening by X-ray fluorescence and dedicated methods for mercury, for lead, cadmium and hexavalent chromium, for brominated flame retardants, and for phthalates. Two consequences follow, and both matter commercially:

1. X-ray fluorescence screening cannot see phthalates at all. It is an elemental technique. A report consisting solely of an XRF screen, issued after the four phthalates joined the restricted list, does not address four of the ten substances. For flexible PVC insulation and over-moulds — the softest, most plasticised parts of your harness — those four are precisely the ones at risk.
2. XRF does not speciate. It reports total chromium, not the hexavalent form that is actually restricted, and it reports total bromine, not the specific restricted flame retardants. A screen showing bromine present is not a failure; it is a trigger for a confirmatory method.

Check what was tested. A report lists test items — often as "black plastic", "silver metal", "yellow metal". Count them against your homogeneous-material list. A harness with twenty materials and a report with three test items covers three materials. That is not a criticism of the laboratory; it is what was submitted.

Check the identity chain. The sample description on the report must be traceable to a part number that appears on your bill of materials, ideally to the material supplier's own part number. Reports describing "cable sample" prove something about a piece of cable somebody once had.

Check the laboratory and the date. An accredited laboratory (ISO/IEC 17025 scope covering the methods used) and a report number you can verify with the laboratory directly. Set an internal age policy — many buyers accept reports up to twelve months old for stable materials and require re-test on any change — and write the policy into the contract instead of arguing case by case.

The same three questions apply here as to any certificate in this trade: who issued it, in whose name, and until when. CMH's listing for this Shenzhen harness supplier states plainly that no EU or US market-entry product certificates are on file, and tells buyers to check exactly those three fields on any document they are shown. Treat substance evidence the same way — the reasoning is set out in more depth in the sibling article on issuer, holder and validity on a harness supplier's certificates.

One more thing worth saying plainly, because it saves an unproductive conversation: substance analysis is not a production-floor function anywhere in this industry. The bench a competent harness shop runs — terminal cross-section analysis, tensile and insertion-force testing, withstand-voltage and insulation checks, salt spray, continuity — is built to verify mechanics and electricals, and that is what it is for. Chemical analysis happens at a laboratory. So the right ask of a harness supplier is not "do you test for these substances", it is "which laboratory reports do you hold, per material, from which of your upstream suppliers".

The per-part document pack

This is the pack to request, structured so it can be checked in an afternoon rather than argued about for a month:

1. A bill of materials by part number — every wire, terminal, housing, seal, tape, sleeve, label and compound, with the material supplier named for each.
2. A material declaration per line item, issued by the party that made that material, on that party's letterhead, naming its own part number.
3. The laboratory report referenced by each declaration, with report number, laboratory name, accreditation, issue date, test items and methods.
4. An exemption schedule: which line items rely on which numbered exemptions, and each exemption's expiry.
5. A candidate-list statement, against a named list version and date, identifying any article in the assembly containing a listed substance above the 0.1% threshold — stated per article, not per shipment.
6. A change-control undertaking: no substitution of wire, terminal, compound or subcontracted operation without written notice and refreshed documentation.
7. A named contact at the supplier who is responsible for this file, because the sales contact will change.

Item 5 is where the most common technical error hides. In a complex object, each component article is assessed against the 0.1% threshold in its own right — the threshold is not diluted across the finished assembly. A brass terminal is an article. A length of insulated wire is an article. Working the percentage out against the mass of the whole harness produces a comfortable number and the wrong answer.

Building it into the order, not chasing it afterwards

Substance documentation is cheap at quotation and expensive at customs. Fold it into the commercial documents:

• Put the requirement in the RFQ, so the price you compare includes the work. Suppliers who have this material to hand will say so; suppliers who do not will go quiet, which is also information.
• Make first-article approval conditional on the document pack being complete. A shop that dispatches samples quickly can usually assemble the paperwork in the same window if you ask at the same time.
• Write a substitution clause with teeth. Wire supplier, terminal part number, compound and any subcontracted moulding are all locked; changing one triggers new documentation and a new first article. On a 1,000-piece minimum order, a mid-run reel change is routine unless the contract makes it not routine.
• Set a re-declaration cadence — annually, or on any list update, or on any change of material source, whichever comes first.
• Decide who pays for confirmatory testing. Your own spot-check of a production sample at an independent laboratory is the cheapest insurance in this whole discussion. Agree in advance who bears the cost if it comes back non-conforming.

Buyers who already run this discipline for other categories will find the general framework in China import compliance requirements and the market-by-market view in the importing compliance checklist by market transfers directly; the harness-specific part is only the homogeneous-material count.

Common questions

Is a supplier's declaration on letterhead ever acceptable on its own?

For a low-risk item, from a material maker who names its own part number and the list version, and who will provide the report on request — often yes, as part of a documented risk-based approach. What is not acceptable is a declaration from the assembler covering materials the assembler did not make, with no upstream evidence behind it. The assembler can only declare what it was told; ask to see what it was told.

Can I just require the supplier to indemnify me instead?

You can, and you should have the clause, but it does not discharge the obligation. Authorities act against the entity that placed the product on the market. An indemnity from a supplier with modest registered capital is a commercial remedy, not a compliance strategy — check the registered capital on the business licence before you decide how much weight the clause carries.

What changes if the harness ships as a spare part rather than inside equipment?

The analysis changes, sometimes helpfully and sometimes not, depending on the category and on how the part is placed on the market. Do not assume spares are outside scope. Get the specific answer for your product category from a compliance adviser before you build a programme on the assumption.

How do I handle a supplier who genuinely cannot produce material-level documents?

Two workable routes. Either you nominate the wire, terminal and compound sources yourself and obtain the documentation from those makers directly — practical because they are usually larger and better documented than the assembler — or you fund the testing yourself, at an accredited laboratory, and treat the result as your own evidence. The one route that does not work is accepting a blanket letter and hoping.

What to ask your supplier next

• Can you send a bill of materials by part number with the material supplier named for every line?
• For each line, do you hold a declaration from the material maker, on their letterhead, with their part number?
• Which laboratory reports sit behind those declarations, and can I have the report numbers to verify with the laboratory?
• Which metal parts rely on an exemption, which numbered exemption, and when does it expire?
• Which list version and date does your candidate-list statement reference?
• Will you accept a no-substitution clause covering wire, terminals, compounds and subcontracted moulding, with new documentation on any change?
• Who at your company owns this file, and who takes it over when that person leaves?

A shop whose registered scope covers both production and import-export, and which quotes target markets in the US, Canada, the UK, Germany and France — as Huisheng Electronics does on its CMH profile — is a supplier where these questions belong in the first email rather than the fifth. Pair them with the document list in what to ask a China supplier for before your first order, and read the wire-level and workmanship-level requirements alongside them in the sibling pieces on AWM style numbers and choosing a workmanship class for your harness PO. All three ask the same question in different registers: what exactly is in this assembly, who says so, and what document proves it.