I'd check the grounds through out the car and clean & coat them. The best one to start with is the one that ground that circuit. Look for it in your Bentley or Cabby Info.
I think you have a bad ground somewhere making the circuit will draw too much resistance. Look for excessive heat scars on any related wires and maybe test with a meter on different points in the harness to see what it's running at.
Keep a fire extinguisher in the car.