Checklist
Military cable harness testing checklist
A harness that passes a buzz-through is not a harness that has been tested. This is the sequence we follow on naval and defence assemblies, and what each step is looking for.
Before any electrical test
Check against the current drawing. Wiring schedule, connector part numbers, pin assignments, backshell types and overall lengths, checked against the released revision. Do not check against the last harness you built. Most harness faults found at acceptance come from building to the wrong revision. Poor workmanship is less common.
Inspect the terminations. Crimp height and pull-off where crimped, solder wetting and absence of wicking where soldered, no nicked strands, no exposed conductor beyond the specified length. A crimp that looks acceptable and was made with the wrong die will pass continuity and fail in service under vibration.
Check screening and bonding. Screen continuity through to the backshell, 360° termination where specified, no pigtails where the drawing prohibits them. On naval EMC-critical assemblies this is frequently the difference between a compliant and a non-compliant install, and it is invisible to a continuity test between pins.
Confirm marking. Wire and harness labels must be legible, correct, durable in the working environment and consistent with the schedule. A label that is present but wrong fails.
The electrical sequence
Continuity, end to end, every core. Point to point against the schedule, on every conductor. Record the measured resistance as a number. Contact resistance creeping up across a batch points to a crimp tool problem, and you want to catch it on unit three, long before unit thirty.
Isolation between every conductor pair, and to screen and shell. This is where reversed or transposed cores are caught. A harness can be perfectly continuous and completely wrong.
Insulation resistance at the specified test voltage. Applied between conductors, and between conductors and the screen or shell, and held for the full specified dwell time. Record the value and the ambient conditions; insulation resistance is temperature and humidity dependent and a number without conditions is not a result.
Dielectric withstand where the specification calls for it. Always run it after the insulation resistance test. A withstand test on an assembly with an undetected insulation fault can turn a repairable fault into a destroyed harness.
Screen transfer and bonding resistance where EMC performance is specified. Measure it; a visual check cannot tell you.
Fibre-optic assemblies
End-face inspection before anything else. Under magnification, every connector, every time. Contamination is the dominant cause of fibre loss and mating a dirty ferrule can damage the one it mates with.
Insertion loss against the link budget, measured at the operating wavelength. Check that the tester is set to it and not left on its default.
Return loss where reflection matters to the system.
OTDR trace for anything long enough for the location of a fault to matter, retained as a baseline. A trace taken at acceptance lets you diagnose a fault two years later. Without it you are guessing.
Environmental and mechanical, where specified
Naval and airborne assemblies frequently carry environmental requirements that a bench test does not touch: vibration, thermal cycling, salt fog, or ingress protection at a stated rating. These depend on the specification. Do what the contract says, and never use a bench check in place of a qualification test.
If a harness has been qualified, and not just tested, say so clearly in the paperwork. Qualification demonstrates the design; acceptance testing demonstrates the individual unit. Conflating them in a report is a finding waiting to happen at audit.
Mechanical checks that belong on every unit: strain relief engaged and correctly sized, bend radius respected at every fixing, clamping at the specified intervals, and connector keying confirmed so a unit cannot be mated wrongly under time pressure in a dark compartment.
The documentation is part of the deliverable
For defence and PSU work the test evidence is as much the product as the harness. Each unit should ship with the procedure it was tested to, the measured results with instrument identification and calibration status, the ambient conditions, the operator, and the date.
Record measured values. A tick in a box is not a result. A file of pass marks tells you nothing about drift; a file of numbers shows a batch trending toward a limit before any unit fails.
Where an assembly is a reverse-engineered replacement for an imported item, the pack should also carry the investigation record: what the original measured, what was substituted, and the equivalence rationale. That record is what lets you defend the substitution, beyond showing that it works.
Sources & basis
What this is based on.
- Vebix Automation build and acceptance practice on naval electrical and fibre-optic cable assemblies, including flask and turbine cable assemblies for submarine and torpedo systems and cable casing, flange and coupling work for Indian Navy ship systems.
- Test sequencing follows general electrical acceptance practice: continuity and isolation before insulation resistance, and insulation resistance before dielectric withstand.
Published 16 August 2026. Last revised 16 August 2026. Corrections to sales@
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