Do you have any ideas what I could look at myself for a quick fix?
Two things come to mind here – A bad dash control switch or a bad diverter door motor in the dash. The diverter door or blend door motor as it is sometimes called diverts the airflow from the blower motor to the desired vent location inside the vehicle.
Either this motor is not getting the signal from the dash control switch or the motor is just not operating in that mode.
I have seen pencils and other debris fall down the defrost vents on top of the dash and get lodged in the diverter door motor causing the defrost selection not to function.
Both of these items can be tricky to test and not easy to get to, so I am not sure how mechanically inclined you are and what testing and repairing you can do yourself.
Please share this with your friends,