Pontiac Repair: Heater malfunction - 1997 Grand Prix w/ 3.8 L V-6, electric actuator, three knobs

Question
My wife's 1997 Grand Prix is NOT producing adequate heat for heater or defrost.
Things I've noticed:
When first turned on, the fan motor makes a squealing and stuttering sound. (My guess is that a air flow direction valve or door is not opening and rubbing the fan).
Normally the heater in the GP is more then sufficient.

Recent repairs:
Fan motor was replaced about 2 years ago.  A different mechanic "thought that there were leaves in there" and did no repairs.

Any ideas or direction to start?

Thanks you

Answer
Hi Gene:
First off is the an automatic a/c system meaning digiatal diplay or is it manual controls with three knobs on the control head. If it's an automatic system you could have a temp sensor in the hvac box that's bad not allowing full hot. I think you have 2 differnt issues here. The fan can't rub on any of the doors. Either there is debris in the motor again or the motor has gotten water in it. on that car there is a water barrier that falls off and allows water to get into the fan motor. The deflector is under the cowl where the wiper arms are. As for no or little heat it could be a door issue that the door on that car is driven by an electric actuator. if you tun on the A/C and turn the temp setting to full cold will it blow cold air or luke warm like the heater? if so that is a good indication of an door problem. If it goes cold it doesn't rule the door out it could be binding when it goe towards the hot side but the fact that is does change temps would not necessarily indicate an actautor issue.. You could be low on coolant in the engine or the heater core could be partailly plugged and not allowing the coolant to flow though the heater core. make sure the coolant if full when it's cold and run the car untill up to operating temp and feel the heater hoses. one should be really hot and the other a bit cooler if so then the coolant is flowing though the core okay if they are cold/cool or are both about the same temp I would say you could have a plugged core. if it's plugged you can take off the hoses and back flush the core with a graden hose that usually fixes it.  Hope it gives you a place to start to look.