since i already have to change the heater core............my heater does not blow the air in the volume it used to. the car is parked undercover and the cowl is not full of tree junk, is there any other parts that can wear out such as switches?
You need to approach this like haing dim headlights. First make sure the electrical system is in good condition (battery and alternator voltages). Measure the voltage at the motor and at the battery and see what the difference is. If it's a big drop then the blower will spin slower (also check the ground connection).
If there is a big voltage drop then wire in a relay similiar to what is done for the headlight wiring upgrade. You could track down where the different voltage drops occur but it's how far you want to go with it and whether you are concerend about it being stock or not.
I would also look too to see how bad any of the seals or gaskets are on the heater assembly. From age and exposure to things they deteriorate and instead of the air being pushed out the interior vents there is a lot of leakege elsewhere like behind the dash and the vents do not have as much airflow coming out of them.
Also make sure any vaccum doors are not partially shut and are sealing properly.