Custom Cable Assembly Supplier Checklist: 12 Questions to Ask Before You Send an RFQ

Last March a purchasing manager sent us a six-page drawing package. She had already collected four quotes. The prices sat within 8% of each other. All four quotes named a different connector series.

Nobody had asked her what the harness plugs into.

That is the problem with most supplier checklists. They are written to protect the buyer from blame, not to find a supplier who can actually run the job. Do you have ISO 9001. Do you have a quality policy. Can you sign our supplier code of conduct. None of those answers tell you whether your 300-piece order ships on the 14th, or whether your crimp height will drift by week three.

The twelve questions below are the ones we would want a buyer to ask us. For each one: why it matters, what a good answer sounds like, and what should make you walk away.

Why most supplier checklists fail

A checklist that asks about certificates tells you who has a document control clerk. A checklist that asks about process tells you who can build your part.

There is a second problem, and it is less obvious. Long questionnaires select for size, not skill. A 40-page supplier survey is easy for a company with a QA department and close to impossible for a 60-person shop with excellent hands. If your shortlist gets decided by who can fill in the form fastest, you are optimizing the wrong variable.

Keep it to twelve questions. Ask them on a call, not by email. Listen for specifics, not adjectives.

The twelve questions at a glance

Block 1: Capability and fit

1. Do you actually build harnesses like mine, or would I be your first?

Being a supplier's first customer in a new category sounds flattering. It means you are funding their learning curve, and the learning curve gets paid in your scrap.

A good answer names your product category without prompting and volunteers two or three failure modes common to it. If you build self-service kiosks, they should ask about the door-sensor cable that gets flexed twenty times an hour. If you build battery storage racks, they should ask about voltage rating and temperature derating before they ask about price.

A weak answer is "we do all kinds of cable assemblies, from automotive to medical." Universal capability usually means no line is tuned for your category. It also usually means the quote was generated from a price-per-pin formula.

2. Which parts of my harness do you make in-house, and which do you buy?

Almost nobody makes everything. That is fine. The problem is when the outsourced steps are invisible in the lead time you were promised.

Ask the follow-up: "if overmolding is outside, does the 15-day lead time include the round trip?" The answer tells you whether the number you were given was built from a schedule or from habit.

3. What is the smallest order you shipped in the last 90 days?

Ask about MOQ policy and you get a marketing answer. Ask about actual shipments and you get a fact.

A good answer is a number, a product, and a reason. "Forty pieces of a control-panel harness in September. We took it because the customer gave us a twelve-month forecast and the terminals were already in stock."

That sentence contains three signals: a real quantity, a real condition, and a real reason. The condition is more important than the number. Any factory can accept 40 pieces once. The question is what makes the 41st piece possible next quarter.

"Our MOQ is 1,000 but we are flexible" is a red flag, not a reassurance. Flexible means no standard process. No standard process means every small order gets negotiated from scratch, which means your lead time is unpredictable even when the price is not.

Block 2: Engineering and documentation

4. Who reviews my drawing before the quote?

If the quote comes from a sales desk, the price contains an invisible allowance for rework. Somebody has to discover that your drawing has two different crimp terminals specified for the same circuit. If it is not an engineer before quoting, it will be an operator after cutting.

A good answer gives you a role, not a department: "our process engineer reviews every new drawing and writes the DFM notes before sales prices it."

Here is the counterintuitive part. A quote that arrives in six hours with zero questions usually means nobody opened the drawing. Fast is good. Fast and silent is not.

5. What happens when my drawing is ambiguous?

Most drawings are ambiguous, and the gaps are predictable. These five items are missing from a large share of the drawings we receive:

• How the shield is terminated: one end, both ends, or 360 degrees to the shell
• Label position, content, and material
• Required pull force per terminal (or a reference to the terminal datasheet)
• How branches are fixed and whether a breakout is molded or taped
• Packaging: bulk bag, individual bag, or box with divider

A supplier who has built your type of harness will raise at least three of these before quoting. That is not diligence, it is pattern recognition.

"We will follow your drawing exactly" sounds like compliance. In practice it means every gap becomes your liability. The right answer is a short list of questions, plus a note on which assumption they would use if you do not reply.

6. Can I see the first article inspection report before production?

First article inspection is where a drawing becomes a process. If you cannot see it before the run, you are inspecting after the money is spent.

If the answer is "that is internal documentation," ask one more question: then how do you know the first piece was right? The reply will tell you whether inspection exists as a process or as a folder.

Block 3: Quality and traceability

7. What is your 100% inspection actually inspecting?

"100% inspection" is the most abused phrase in this industry. For a lot of factories it means 100% continuity testing. Continuity proves that two ends are connected. It does not prove the connection will survive a year of vibration.

Continuity cannot catch:

• A cold crimp that still makes contact today and fails at month four
• Insufficient pull force from a worn die
• A partially inserted terminal sitting on the retention lance instead of behind it
• Insulation pushed into the crimp barrel, which passes electrically and fails mechanically

A good answer separates the two numbers instead of merging them: what is 100%, and what is sampled. Any supplier who cannot split that sentence has not thought about it, and a supplier who has not thought about it is not inspecting, only testing.

8. Which tests, which machine, to which standard?

Vagueness here is expensive. "We test everything" is not a specification.

You do not need all six on every part. You do need to know which ones apply to yours, and you need the answer to name a standard. A supplier who says "per A-620 Class 2" knows the language. A supplier who says "good quality" does not.

9. Can you trace a failed harness back to the crimp batch?

Suppose 500 harnesses ship and three fail in the field. With batch records you replace fifty. Without them you replace five hundred, or you argue about it for a month.

Traceability means the traveler carries date, operator, machine number, terminal reel number, and applicator ID. Ask to see one. Not a sample of one that was prepared for a customer audit — one from last week.

This is also the question that separates a factory from a trading company. A trader can produce a certificate. They usually cannot produce a traveler.

Block 4: Commercial and continuity

10. What is in the quote, and what triggers a re-quote?

A single lump price is comfortable for the buyer and useless six months later. You cannot tell whether you are paying for a connector or for someone's overhead, and you cannot argue about a price increase you cannot decompose.

11. What happens if copper moves 15%?

Copper is the one input nobody controls. It has moved more than 20% within a single year more than once in the past decade.

A good answer has three parts: a stated validity window on the quote, a threshold that triggers adjustment (commonly plus or minus 5% on the copper index), and whether the price can be locked for a committed volume.

A weak answer is "our price is fixed" delivered without a validity date. Fixed until when? Fixed against what? That price will move the moment you place the second order, and the move will be a surprise because nobody wrote the rule down.

12. Who do I call when something breaks at 11pm before a line start?

This question is uncomfortable and that is why it is worth asking. Every supplier is responsive during the quotation stage. The ones worth keeping are responsive during a production stop.

A good answer is a name, a direct channel, and a response commitment. "You have my mobile. If it is a stop-line issue, call any time; I will get an engineer on it within two hours and I will tell you what we found before we tell you whose fault it is."

That last clause is the whole answer. Suppliers who lead with fault-finding cost you days.

The red flags that matter more than the answers

Answers can be rehearsed. Behavior is harder to fake. Six signals are worth more than a stack of certificates.

What a weak answer sounds like next to a strong one

How we answer these twelve questions

Since it would be strange to publish a test we are not willing to take, here are our own answers, shortened.

On capability: we build custom cable assemblies and wire harnesses for equipment builders. Kiosks, energy storage, 3D printers, displays, appliances, control panels, trailers. We do not build automotive harnesses, and we say so on the first call, because a supplier who chases every category is a supplier who is mediocre in all of them.

On the smallest order: last month we shipped a 40-piece control harness and a 900-piece kiosk harness in the same week, on the same line, with the same test procedure. That is not generosity. Small and large orders use the same setup; the only difference is how long the run lasts.

On inspection: every piece gets 100% continuity and short testing and 100% visual inspection by a person, not a camera. Pull force is measured on the first and last piece of every batch plus a sample in between. We do not claim 100% pull force on every terminal in a 5,000-piece order. Nobody does. A supplier who tells you otherwise is either lying or building ten pieces a day.

On quoting: drawings go to a process engineer before they go to sales. You get the price and a short DFM note in the same email, usually within 24 hours. If we have questions, you get the questions instead of a number, because a number built on a guess becomes a change order later.

On traceability: every batch carries a traveler with date, operator, machine, terminal reel, and applicator ID. Ask us for one on your first order. We will send a photo of it with the FAI.

If you want to test us with the other seven questions, the fastest way is to send a drawing.

Frequently asked questions

How many suppliers should I quote?

Three is enough, and four is usually one too many. Beyond three you stop learning anything new and start optimizing on price alone, which is the wrong variable for a part that can stop a production line. What matters more than the count is that all three receive the same drawing revision and the same quantity break.

Is the lowest quote usually the best value?

Not usually, and the gap is rarely in the unit price. It shows up in the second order: a supplier who won on price often won by skipping the drawing review, so the first batch needs rework, or by quoting a connector they cannot source consistently, so the second batch has a substitution you did not approve. Compare total landed cost on three orders, not one.

Do I need to visit the factory in person?

For a first order under a few thousand dollars, no. A video call walking the line is enough to confirm that the equipment exists and that someone can explain it. For a program you expect to run for years, or a part with safety implications, visit. Look at the test bench, not the reception area.

What if I do not have a drawing yet?

Send what you have: a sketch, a photo of the assembly, a competitor's sample, or a list of connectors and lengths. A good supplier will turn that into a drawing for you to approve, and will tell you which decisions are still open. What you should not accept is a quote built on an assumption nobody wrote down.

How long should a quote take?

Two to five working days for a new custom assembly is normal, because it involves a drawing review and a material check. Twenty-four hours is possible when the part is simple or the components are already in stock. A quote in two hours on a complex harness is not speed, it is a formula.

Should I ask for samples before the first order?

Yes, but ask for the right sample. A hand-built sample proves the design is possible, not that the process is repeatable. Ask for a sample from a production run, with its inspection record, and ask what the sample's crimp height was. If the sample and the record do not match, you have learned something important for free.

What is a normal MOQ for custom cable assemblies?

For a factory that specializes in equipment harnesses, 50 to 100 pieces is a realistic floor. Large automotive-tier plants often quote 1,000 to 5,000 because their setup and traceability costs only amortize at that volume. If you are being quoted 5,000 for a 200-piece need, the problem is fit, not price. See our breakdown of what low volume actually costs and why.