94 PA Blower Control Module & fan speed

I am contemplating replacing the module because I think the fan motor speed, especially on defrost or AC mode, is slow. The indicator bars on the dash go all the way up when the climate control is calling for full heat or defrost. I replaced the fan a year or two ago and it helped some.
So, my question is, even though the fan runs, would the module, when it fails, fail completely or could it partially fail and cause the motor to run at less than full speed.
Or, maybe I am expecting to much of the heating system but I want to believe that a luxury Buick would be designed with better heating and defrosting than mine has.
The car has 176,000 miles and other than a couple crankshaft sensors and a water pump, has been fantastic.
Any advise is greatly appreciated because it gets mighty cold and snowy in Minnesota in the winter and I have to get this working better!!

Welcome to AF, very tough to tell what is normal fan speed under these conditions the programmer position controls the blower speed thru the power module, it is possible that an element in the module is bad, or the air could be escaping thru deteriorated seals in the ducting. When the dash control shows it is commanding full blower speed, see if there is 12v at the motor. Lots can happen with a 14 year old car.

It is possible that the evaporator is clogged with debris and needs to be cleaned. Airflow through the system depends on the correct blend door position, as well as, an unobstructed evaporator. Like MAX said; Check the voltage at the fan motor while on high speed, and go from there.