The blower motor may operate erratically and the blower switch operation has a sticky or mushy feeling, the detents almost non existent. Our technicians tell us that the blower switch should be removed and inspected for overheating. This is common if the blower motor is frequently operated on high speed as the current flow through the switch tends to melt internal the components. Also carefully inspect all of the switch connector terminals for discoloration due to overheating and replace as required. A poor electrical contact at the connector will also cause the switch to overheat.