91 pickup electrical questions...

The heater in my truck is doing something werid. The fan will blow on the high setting only. It still heats great, but if i turn it down the fan just shuts off. Does anyone have any ideas why?

Also, i have been wanting to put some speakers in my truck somewhere. I was thinking 5-8 inchs? I upgraded the ones in the front, but having them up front just doesnt give a nice sound. Does anyone have any reccomendations of where to put them... i know there isnt a whole lot of room for them.

My fan was doing the same thing about 5 years ago. I fixed it by replacing some part that goes on the blower motor a resistor or something, someone else may know the name of it.

The fan speed resistor module is bad. It is mounted in the ductwork under the dash, pass. side. Look for a connector w/3-4 wires.