1989 heater fan runs but no air in cab

This is a strange one, for me at least. My heat quit blowing recently. I have had other Chrysler vehicles and most of them had a resistor network to control the fan speed so when the fan quit blowing I figured the fan motor was shot or the resistor network was fried. I couldn't find a resistor, so I checked the voltage going into the fan at different speed settings. It showed battery voltage ~ 14 volts, no matter what the setting, and went to 0 volts when the heat was turned off. Next I pulled the fan, and it seems to be working perfectly, turning on and off with the heat. I am mystified.

I have a Chilton's manual, but it's pretty useless. Is there a damper that controls the amount of air when the fan speed control is changed?

Any ideas would be appreciated, it's darn cold right now in NC.

the blower motor resister is behind the glove box

Thanks!

Thank you for your quick response.

I will pick a resistor up on the way home and then go from there. I hope it's something simple like that. Every Dodge I've ever owned eventually needed one but they were always in the engine compartment.