burned wiring

I recently replaced the motor, heating element, and all thermostats/thermal cut-offs in my kenmore series 90 dryer. It worked great for about three days and now won’t heat. the motor no longer cuts off and the heating element is fine but the red wire leading to the heating element is charred and slightly melted. I can fix the wire and replace the connector but am concerned that it may happen again. What would cause this?