heater selector switch follow up

if you remember my heater fan switch was heating to the point where you would burn your finger on the switch once it was turned on. I had a new switch, installed it and sure as [email protected]# the old one was burned, the phenolic back panel was dark brown, and the metal housing had signs of heat/fire expulsion around the sides. what could cause this????? I did have a window leak that I have fixed, but the switch is so far away from the path of the water I don't think that was it. I am concerned because I think the new switch might be building up heat too. I don't know why? I am the second owner of this car. I bought it from a little old man so I know no wires were cut, and every gauge I added went right to the fuse block with a fuse, so I am fairly certain there are no open wires or cut and chafed wires. any help would be great, thank's in advance, mike and the car is a 70 el camino by the way