That is one of the problems of an over engineered car. Spade connectors fatigue and the connection gets hot. What does the other side of the plug look like? Is there a wire or does it plug directly into the resistor?
If there is a wire it is easy, Separate the wire that hooks up to the blue wire and connect directly with a larger spade connector. If it plugs directly into the resistor then the plug is self will have to be modified to allow the replacement of the fatigued connector in the plug.