One-sentence answer: The sealing difficulty of waterproof wire harness connectors lies where the core wires pass through: every wire must pass through a sealing plug or potting body, and the tolerance of wire diameter combined with the number of cores makes the compression uneven, while water can also penetrate along the wire core by capillary action. Using the CTS Sentinel A28 differential pressure leak detector to compare a master part with the part under test maintains stable judgment on workpieces with relatively large volumes such as multi-core wire harnesses, making it suitable for 100% inspection in batches at wire harness factories.
The same connector may be fitted with wire harnesses of different core counts and different wire diameters. The sealing of a single wire relies on the hole wall gripping it tightly; the fewer the cores, the harder it is to compress tightly, and the process window drifts with the configuration.
Capillary channels exist between the strands of multi-strand twisted wire. Once water enters from the connector end, it travels along the wire core to the other end. Different test timings lead to different conclusions, which is also the most common dispute in wire harness sealing.
In the process where the wire harness and connector are injection molded as one piece, insufficient filling or entrapped air bubbles can form internal cavities that show no abnormality in appearance.
Wire harnesses are subject to bending and vibration over the long term, and the gripping force of the sealing plug and sheath slowly decreases. Factory inspection is the only step that can quantitatively intercept the onset of degradation.
Sealing locations:
Consequences of leakage: water enters the ECU or high-voltage connector along the conductors, causing terminal corrosion, reduced insulation, and signal errors; for high-voltage circuits it may also cause short circuits and leakage alarms, making it a vehicle safety item.
The characteristic of wire harness connectors is that the cavity is extended by the wire harness, so the internal volume is far larger than the connector itself, and there are many parts with a fast cycle:
Yes. The cavity of the wire harness is connected to the wire core ends, and only by sealing the far end can the wire harness itself be included in the test scope. If only the connector side is sealed, the leak point is left outside the test cavity, and the test conclusion is meaningless. A common practice is to plug the end faces one by one with plugs or clamping sealing blocks.
An air tightness test reflects the overall leakage of connected channels and can identify wire harnesses in which a through capillary path has already formed. Simulating the water seepage process in service requires durability tests such as immersion and vibration. The role of the air tightness test is to screen out process defects first at the factory stage.
A separate test program must be created. Changes in core count and wire diameter simultaneously change the cavity volume and the compression state of the sealing plug, so the inflation pressure, stabilization time, and judgment limits all need to be adjusted accordingly. The A28 can store 32 test programs, which can be called up by wire harness model without re-adjusting the machine on site.
In sealing tests for waterproof wire harness connectors, the key is to quantitatively intercept the process fluctuations at the core wire pass-through locations before shipment. The CTS Sentinel A28 uses differential pressure comparison to accommodate large-volume workpieces with wire harnesses, and with one-by-one plugging fixtures and 32 test programs, it is suited to batch 100% inspection and data traceability in wire harness factories with mixed production of multiple models.
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