1997 Other Mitsubishi Models Ventilation System problem

Air Conditioning problem
1997 Other Mitsubishi Models 4 cyl 105000 miles
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1997 Mitsubishi Mirage DE, 105000 miles

I bought a "new" used car this morning (private buyer). In the first 20 minutes of driving I noticed that the knob for turning A/C, heater, defroster worked only in the 1-3 positions. Number 4 did not work (max air). I drove again an hour later and then none of the positions worked..nothing was blowing.

I stopped at AutoZone and they checked the fuses. (nothing wrong with them). He said he could not check the relays because he didn't have a manual online for my car...that I would have to take it to dealership.

I want to know what my first step is. Could it be electrical----switch that powers the fan? (since the 4th position went out first) If not electrical, then could it be the fan motor? What am I looking at in costs or possible problems? Also, do you know if there is anything I could do to make previous owner have to help since it hasn't even been 24 hours since buying the car? (not bought on car lot)

Thanks