I have a 1993 Pontiac Bonneville. Here is the problem I am having. I am experiencing little heat output through all the vents including the defroster. When you turn the fan switch you can hear the motor go through the fan speeds. Could this low air flow be caused by a blockage somewhere? I do not overheat while driving and the heat is great. As I live in Colorado the weather gets pretty cold in the winter and my defroster can’t keep up with the wet snow that freezes to the windshield.

It could be a blockage in the evaporator box due to leaves and trash. I have seen this problem where the blower fan was "wired backwards" on a similar model that caused this problem. (It is a DC motor it will run in both directions depending on how it is wired.) Removing the blower motor MAY be the best way to figure out what the problem is. By looking at the fan motors "Squirrel Cage" you can make sure it is spinning correctly. Also you can see inside the heater housing much better to make SURE there is not a lot of trash or leaves.

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