I too agree it should not be happening - but it might not be the wires. Poor plug connection or a problem with that plug is more likely. Note it is vital when removing these connectors from the plugs to use an appropriate puller, else damage will eventually occur. I use a narrow-tip Visegrip to grip the crimp flange on the metal part of the connectors, which avoids any strain on the vulnerable parts. If you have been pulling on the non-metallic part, then best bet is to replace the wires or at least the ends.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7