A blown fuse is caused by two things, age (Unlikely in your case) or excessive current flow usually caused by a short direct to earth, any half decent spark should be able to track down the cause quickly and cost effectivly, but a siezed/damaged actuator can cause significant enough current flow and heat in the system to blow it too. If you can access the back of the switch either disconnect it or remove the earth line, ensuring you remove the fuse first so you dont short anything out.