If your engine is factory equipped with an alternator (AC), the wiring for the voltage regulator and/or alternator will have a 3-pin plug.
If a DC generator (dynamo) was used at the factory and was replaced at some point with an AC alternator using an external voltage regulator, the wiring often does not use the correct plug. Often cable lugs are tightened onto the contacts, which works, but can come loose quite quickly, so Volkswagen has used a plug for this.
If this plug is used with the alternator, it is also fixed by a clamp, hence the recess on the plug.
The plug is delivered separately, without the spade connectors.
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