Heater Fan problem

I have replaced the fan motor and is working but I have very little air flow. It sounds like it is rumbling and a trickle of air comes out. Can someone please direct me to where I can start looking for the problem.

A lot more info would help, like y/m/m. Have you checked the switch or blower motor resistor?

I am having the same problem on my 1993 Sierra, the motor was rumbling terribly, I had on the "Hi" speed on the fan control. Today I picked the resistor for the speed control.
The QUESTION: Can someone direct me to the location on the resistor. I have seen some that look like they are likely mounted under the dash with a harness plugging into it. The one I picked up for my 93 looks is an open circuit board unit.... does this one mount inside the motor housing?
I hope to tackle this in the morning (to deal with the Minn cold).

Thank you.
Bryan

I found and replaced the blower resistor and also replaced the blower motor. I have a few GM vehicles but I have to say... what a pain. How much more difficult could they make it to do the blower replacement? It is like they built the truck around that blower motor.

I am disappointed in how our car makers make things a pain when it doesn't need to be that way.

Bryan
1993 GMC pickup, 3 fuel pumps, 4 alt, 1 blower motor and resistor
1997 Suburban, 9 fuel pumps, intake mani, injectors, 3 alt
1997 Park Avenue, 2 water pumps, a by-pass line, plenum
1992 Park Avenue, 3 water pumps, injectors, motor mounts, 2 alt