An unused circuit is not automatically a sealed cavity. For a sealed connector designed to accept cavity plugs, specify the manufacturer-approved plug for each unused position, its installation instruction and the exact housing configuration. Record these positions on a controlled cavity map. A spare terminal, short wire stub, dust cap or backshell is not an interchangeable substitute unless the manufacturer documents that construction for the application.
This matters when one housing serves several machine options. The basic model may use four circuits while an optional package uses six. A quotation that names only the common housing leaves the two unused positions undefined. The missing detail can affect material quantities, assembly instructions, inspection coverage and the applicability of environmental evidence.
This guide addresses the depopulated configuration: which cavities intentionally lack working circuits, what closes them, and how that state remains traceable from quotation to service. It does not provide a universal plug diameter, insertion force, leak limit or ingress rating. The responsible designer must approve the exact connector configuration and its intended environment.
Separate five items that are often called a blanking plug
Purchasing language can conceal different functions. Ask suppliers to identify the physical part and its location rather than accept the word “blank.” A rear cavity plug closes an unused terminal or wire entry according to its specified design. A cap protects an unmated connector interface. A backshell organizes the cable exit or provides other documented protection. These items can appear together without performing the same job.
The term dummy contact needs particular care. In this guide it means a proposed non-working contact or terminal used in an otherwise unused position; it is not a standardized part category or an approved sealing method. Require an actual manufacturer part number and instruction if a supplier proposes one. Do not infer sealing performance from the fact that the item occupies space.
On small screens, swipe or scroll sideways to read every column. Keyboard users can focus the table and use the arrow keys.
| Offered item | Question that identifies its function | Evidence needed before accepting it |
|---|---|---|
| Rear cavity sealing plug | Which exact housing cavity and seal variant does it close? | Compatibility reference, drawing and installation instruction |
| Terminal without a working circuit | What seals the rear entry, and why is this construction approved? | Manufacturer-approved terminal, seal and termination arrangement |
| Wire stub with terminal | Where is the free end located and how is it terminated? | Controlled circuit state, end treatment and approved complete construction |
| Unmated interface cap | Which open mating face does it protect? | Matching housing, installation state and documented protection scope |
| Backshell or cable boot | Which routing or protection function does it provide? | Accessory compatibility and assembly requirements; separate cavity treatment |
Treat a molded closed position differently from an open position requiring a plug. If the selected housing drawing identifies a deliberately closed feature, preserve that identity on the map. Do not drill, pierce or populate it because a related housing has a terminal there. The drawing determines which positions are available and how they are designated.
Start with the exact connector, not plug color
A useful selection chain is: housing order code → cavity type and rear seal → approved plug → installation document → verification record. Start at the left. Choosing a loose plug from a photograph reverses the chain and leaves compatibility unproven.
TE's DEUTSCH DT inline catalogue, revision 08-25, page 23, requires suitable plugs in unused cavities and distinguishes N-seal and E-seal applications. Its table identifies 114017-ZZ for both seal descriptions, while other entries are restricted to one. That is a configuration-specific selection table, not a rule that every white plug fits every DEUTSCH connector.
The separate TE 114017-ZZ product record identifies a sealing plug with the internal description size 12/16 and links its product drawing. Use the drawing and relevant housing documentation together. A broad product-family tag or a supplier's shortened description does not establish compatibility with an arbitrary cavity.
For another example, TE's NTSEAL connector FAQ tells users to select cavity plugs by the housing's cavity diameter and configuration. It lists 1.9, 2.0 and 2.5 mm in that selection context. Those are NTSEAL reference choices, not dimensions to copy into a DT, CMC or other connector order.
The procurement implication is to retain full suffixes. A change in rear seal, contact arrangement, cavity geometry or accessory configuration requires a documented compatibility review. “Same family” and “same number of positions” are screening descriptions, not release criteria. If a bidder offers another code, require its mapping before comparing the commercial totals.
Build a population map for every supplied connector half
A wire list usually identifies active circuits well but can leave unused positions invisible. Add an explicit population map to the harness drawing. Give every available cavity a defined state and identify the viewing direction. A photograph can supplement this map; it should not be the only definition.
Use the manufacturer's cavity designations. Do not invent sequential numbers where the drawing uses letters, mixed identifiers or separate contact-size groups. The harness pinout and cavity-view guide explains how to keep mating-face and wire-entry views from being confused. Here the additional task is to make the intentionally absent circuits visible.
Each supplied half needs its own record. A wire-to-board interface can have a harness connector on one side and a fixed header on the other. A wire-to-wire assembly can have different circuit states on its two harnesses. Do not automatically mirror plug quantities across the interface; review the actual supplied parts and approved design.
On small screens, swipe or scroll sideways to read every column. Keyboard users can focus the table and use the arrow keys.
| Map field | What to record | Why the buyer needs it |
|---|---|---|
| Connector identity | Harness reference, manufacturer, full housing code and revision | Links the map to the quoted item |
| View and datum | Mating-face or rear view with latch or key orientation | Prevents a left-right interpretation error |
| Cavity designation | Exact designation from the housing drawing | Connects assembly, inspection and service instructions |
| Population state | Active circuit, approved spare construction, sealing plug or documented closed position | Removes ambiguous empty cells |
| Component identity | Terminal and wire, or exact plug code, as applicable | Produces an auditable material quantity |
| Installation reference | Document revision and applicable step or figure | Defines direction, seating and tool requirements |
| Verification link | Inspection point, evidence record and any applicable test recipe | Shows how the intended state will be checked |
Reconcile the map with the BOM before release. Each open position should resolve to an approved populated construction or the specified closure. Count by plug type, not merely by total plugs, especially in hybrid housings with several cavity sizes. Keep unexplained positions as open engineering issues rather than assuming that the assembly operator will choose a solution.
The DEUTSCH DT complete-BOM guide covers the broader housing, terminal, seal and wedgelock pairing. This population map adds variant control: the same approved connector family may have several deliberately different production configurations.
Make assembly sequence a controlled requirement
Plug installation can depend on access, seal geometry and other assembly operations. Specify the applicable instruction instead of creating a universal “insert last” rule. The work instruction should show what the operator sees at the actual installation stage, including any cover, lock or fixture already present.
Molex's CMC 32Way wire-to-wire panel-mount header application specification, document 5018203231-AS-EN revision B, section 6.2, gives a concrete example. It requires plugs in unused terminal cavities, specifies orientation and places plug installation before terminal population. Its table identifies separate CP 0.6 and CP 1.5 plugs. Apply those instructions only to the covered header configuration; another series may use a different process.
For the buyer, the deliverable is a controlled sequence with inspection access. Ask where a wrong plug, missing plug or incomplete insertion can be detected before subsequent parts obscure the area. An operator instruction should distinguish “present” from “correctly seated,” using the manufacturer's reference surfaces or other specified criteria.
Do not create a generic seating depth from a photograph. Likewise, do not add an arbitrary pull force or probe test simply because it seems reassuring. Inspection tools must be appropriate to the component and approved process. The terminal retention and secondary-lock guide concerns terminal retention; its checks are not automatically cavity-plug acceptance tests.
Keep material staging consistent with the map. Where more than one plug is used, identify each bin by part number and the applicable positions. Color may be a secondary visual aid after identity is established. Record substitutions and mixed packaging as exceptions to resolve, rather than letting operators compensate by trial fitting.
Distinguish assembly inspection from environmental proof
A visible plug is useful evidence of assembly state, but it does not establish an ingress rating. Conversely, a report for a fully populated connector may not answer what happens in a different configuration containing many plugs. The question is whether the offered configuration falls within the documented qualification scope.
Ask for the specimen description, not just the report's pass statement. The description should allow a reviewer to connect the tested housing, seal, plugs, wires, accessories and mating state to the production map. If the report covers a representative configuration, request the engineering rationale for applying it to the quoted variant.
The sealed-harness pressure-decay guide addresses the separate question of leak-test boundaries, correlation and acceptance. This article does not choose a pressure or leak limit. A production screen must have an agreed purpose and method, and its fixture must not conceal the feature it is intended to examine.
For example, ask whether the fixture temporarily covers an otherwise exposed rear area. If it does, identify that boundary in the test record and determine which defects remain detectable. This is an evidence question, not an instruction to modify a fixture or conduct an unapproved test. The supplier's quality and engineering teams should establish the method.
Also separate the assembled, unmated shipping state from the installed, mated service state. A connector may be closed at its unused rear entries while its mating interface remains exposed. Specify any required interface cap independently, with its part identity and protection scope. Avoid describing the entire disconnected assembly as waterproof solely because its unused cavities contain plugs.
Compare a partially populated option with the full variant
Consider a hypothetical procurement example, not a tested product or recommended electrical design. A platform uses an eight-position harness interface. Variant A uses six active circuits and two approved cavity plugs. Variant B uses all eight circuits. Both are proposed around the same housing, but their released population maps and material quantities differ.
The following is a simplified Variant A record. Positions 1–8 and Plug P are hypothetical identifiers, not a real housing numbering scheme or orderable plug. Replace them with the actual drawing designations and approved part numbers before use.
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| Hypothetical position | Variant A state | Required identity | Count contribution |
|---|---|---|---|
| 1 | Active circuit C1 | Approved terminal and wire for C1 | One circuit assembly |
| 2 | Active circuit C2 | Approved terminal and wire for C2 | One circuit assembly |
| 3 | Active circuit C3 | Approved terminal and wire for C3 | One circuit assembly |
| 4 | Active circuit C4 | Approved terminal and wire for C4 | One circuit assembly |
| 5 | Active circuit C5 | Approved terminal and wire for C5 | One circuit assembly |
| 6 | Active circuit C6 | Approved terminal and wire for C6 | One circuit assembly |
| 7 | Unused; specified closure | Approved Plug P for this cavity | One Plug P |
| 8 | Unused; specified closure | Approved Plug P for this cavity | One Plug P |
This map reconciles six circuit assemblies plus two plugs to eight available positions. It does not approve the mating half: separately check its contact population and interface drawing. If a contact remains opposite a plugged position, obtain confirmation that the selected plug construction and mating geometry permit that combination. Do not assume every rear plug allows every opposing contact arrangement.
The buyer's initial request says only “eight-way sealed connector.” Bidder One prices eight contacts and eight wires. Bidder Two prices six circuits but omits the closure components. Bidder Three identifies six circuit assemblies and two specified plugs, while listing the applicable installation evidence as a separate deliverable. These offers cannot be compared as equivalent without clarifying the requested variant.
For Variant A, the review checks that the two unused positions are identified in the correct drawing view, each plug is mapped to its cavity, and the proposed assembly sequence matches the component instructions. It then asks whether available qualification evidence covers this configuration. No leak result or rating is assumed from the number of filled positions.
On small screens, swipe or scroll sideways to read every column. Keyboard users can focus the table and use the arrow keys.
| Hypothetical offer difference | Technical question | Purchasing disposition |
|---|---|---|
| Eight contacts and wires quoted for the six-circuit variant | Are the extra circuits a documented requirement or an unintended configuration? | Clarify the design before comparing cost |
| Six circuits with two positions left undefined | What closes each unused opening? | Hold release until the map and BOM are complete |
| Two visually similar substitute plugs | What manufacturer evidence establishes compatibility? | Evaluate as a proposed change, not an automatic equivalent |
| Correct plug identities but only a fully populated test specimen | What supports applying that evidence to the depopulated variant? | Request the qualification scope or engineering rationale |
| Correct map, process and applicable evidence | Are deliverables, traceability and exceptions aligned? | Continue the normal technical and commercial review |
The example illustrates a decision method, not a promised cost saving. A plug's unit price does not capture engineering review, inspection, variant handling or any additional validation. Ask bidders to separate recurring assembly cost from one-time development and evidence work so differences remain explainable.
Send your connector population map and proposed plug BOM to SINAWATTS for a scoped sourcing inquiry. Include unresolved compatibility questions so the response can identify required evidence rather than assume an approved construction.
Preserve the configuration through rework and service
A spare circuit may later become active, or an active circuit may be removed from a lower-feature variant. Either change alters the population map. Control it as a documented configuration change rather than an informal terminal-removal operation.
Molex's CMX application specification AS-560065-002 revision E1 provides a useful product-specific boundary: section 4.3 requires a removed seal plug to be replaced with a new one. Its assembly section also distinguishes plug sizes and their placement. These instructions support a simple purchasing question: what replacement materials and approved rework instructions accompany this exact configuration? They do not establish a universal reuse rule for unrelated connectors.
A change record should identify the affected harness revision, removed component, replacement construction, instruction revision and required inspection or testing. Preserve the earlier state for traceability. Do not edit an old inspection record so it appears to have covered the new population pattern.
Service packaging matters as well. If optional circuits will be added later, specify the approved kit contents and the information needed to identify the vehicle or equipment variant. A loose bag of visually similar contacts and plugs is difficult to reconcile with a controlled map. Request separate identifiers for any parts whose appearance does not uniquely establish compatibility.
When damage or contamination is discovered, obtain the applicable manufacturer disposition and project approval. Do not conceal an unresolved seal issue with grease, adhesive, tape or an unapproved filler. This guide does not authorize repair materials or define a permissible number of insertion and removal cycles.
Reconcile installed quantities and service quantities separately
A cavity map defines what belongs in one released assembly. The purchase order may also include loose replacement parts, development samples and an agreed allowance for the manufacturing process. Keep those quantities separate. Otherwise, an apparent excess of plugs can hide a missing installation requirement, or a service kit can be consumed on the production line without an obvious discrepancy.
Use a simple planning calculation for each approved plug code: installed quantity equals the number of applicable unused positions per connector, multiplied by the number of those connectors per harness and the ordered harness quantity. Calculate each harness variant separately before combining demand. This is a purchasing arithmetic check, not a substitute for the manufacturer's compatibility table.
For a hypothetical material reconciliation, suppose an approved map calls for three identical plugs in one connector per harness and the order contains 120 identical harnesses. The installed requirement is 360 plugs. If the order additionally calls for 20 separately packaged service plugs, the specified delivery requirement becomes 360 installed plus 20 loose. Any manufacturing allowance is another agreed quantity; do not invent a percentage or count that allowance as installed product.
Now consider a revision that activates one previously unused position. The affected variant requires two installed plugs instead of three, but also needs the newly approved terminal, wire and termination process. Reducing the plug order alone does not release that revision. Update the map, BOM, work instruction and verification coverage together, while retaining a clear split between old and new production.
At first-article review, compare three records: the intended map, the issued material list and the observed finished configuration. A total quantity can match while the locations are wrong. Review locations directly, including any cavities obscured by covers after assembly. Obtain the necessary in-process evidence at the agreed inspection stage rather than dismantling finished connectors without an approved procedure.
For shipment records, identify which revision was built and how loose service materials are labelled. If two variants look identical externally, the harness label or accompanying controlled record should distinguish them. This lets receiving and service personnel select the correct population map without guessing from visible wire count. It also makes a future change assessment specific to the affected assemblies.
Release a quotation with clear evidence and exceptions
A complete RFQ can remain concise. Attach the controlled connector drawings and population maps, then ask each supplier to respond to the same evidence fields. Use the OEM and ODM sourcing-coordination page to organize a specification inquiry; any offered assembly, inspection or testing capability needs confirmation in the actual quotation.
The release package should contain five linked decisions. First, engineering approves the housing and closure compatibility. Second, the BOM reconciles every mapped position and plug quantity. Third, the manufacturing instruction identifies installation and inspection requirements. Fourth, qualification or production-test evidence is evaluated against the offered configuration. Finally, purchasing records the agreed deliverables and remaining exceptions.
For each exception, assign an owner and a release consequence. A missing supplier price can remain a commercial question; an undefined closure in a required sealed configuration is a technical release issue. This distinction prevents a low quoted total from obscuring missing engineering content.
Ask for document titles and revisions rather than an unsupported “compliant” checkbox. If the manufacturer updates an instruction, review whether the change affects the approved build. If a supplier changes a plug source, housing suffix, seal or assembly step, require notification before affected production is released under the old evidence package.
Receiving inspection should verify the agreed configuration and records at the project-defined sampling level. This guide does not invent an inspection frequency. Establish that frequency using the contract, supplier controls and application risk. Keep any nonconforming shipment identifiable until an authorized disposition is recorded.
Buyer FAQ
Can an unused cavity simply remain empty?
Only if the exact connector design and applicable documentation permit that state for the intended use. For the cited DT and CMC examples, unused open cavities require the specified sealing plugs. Identify the housing and cavity type first; do not assume that a family described as sealed closes every unpopulated entry automatically.
Is a dummy contact equivalent to a sealing plug?
Not by terminology or appearance. Ask what “dummy contact” means in the offered BOM and what closes the rear opening. Accept a terminal-based spare construction only when the manufacturer and responsible designer support that exact arrangement. Otherwise, request the approved cavity closure instead of improvising one.
Can I use the same plug in every connector from one brand?
No such compatibility should be assumed. Match the complete housing, cavity and seal configuration to a documented plug identity. The cited manufacturer examples distinguish seal variants or cavity sizes within their own product ranges. Color can help inspection after the part number is controlled; it does not replace compatibility evidence.
Does installing plugs make an unmated connector waterproof?
It does not establish that claim. Rear cavity closure and protection of the open mating interface are separate questions. Review the documented mating state, accessories, test conditions and qualification scope. Specify any required interface cap independently, and avoid extending a rating beyond its supported configuration.
Must plugs always be installed before terminals?
Follow the exact application instruction. The cited CMC header specification requires that order, but this is not a universal rule for all connectors. The supplier should show the applicable sequence and an inspection point where the specified plug identity, orientation and seating can actually be checked.
Can removed plugs be reused during a circuit change?
Check the manufacturer instruction and approved service process before deciding. The cited CMX instruction requires replacement of removed plugs. Other products need their own documented disposition. Update the population map and record the replacement construction; a previous inspection result does not automatically cover the changed assembly.
What affects price, MOQ and delivery for a depopulated harness?
The actual housing and plug identities, circuit population, quantities, packaging, traceability, inspection and required evidence can affect the quotation. Request current commercial terms for the defined build and separate development work where applicable. This guide provides no stock, price, MOQ, lead-time or SINAWATTS testing-capability guarantee.
Send a controlled cavity-plug RFQ
Send the housing codes, cavity maps, plug identities and evidence requirements to SINAWATTS. Include the intended environment, mating and shipping states, quantity, delivery requirement and any proposed substitutions. A clearly defined depopulated configuration gives suppliers a concrete scope to confirm and makes technical exceptions visible before the order is released.