No air

2007 toyota yaris, we have had no cool or hot air blow out when we turn on the fan on our way home the last two times we went somewhere. On the way there when the car is cold it has been fine, but the other day when we needed the defroster there was no air and my wife got to drive and wipe the windows clean as they fogged up. Goodyear checked them today and said nothing was wrong, bring it back when it acted up, that’s not much help. heat is still hot and air is still cold when it does work.

Does any ambient temp air blow out? Or is the problem that plenty of air blows out, but it is not the correct temperature? The blower motor and its relay and the vent door motors/mechanisms should be considered as potential sources.

Is the blower fan motor not operating or is this a case of the blower can be heard running but no air will come out of the dashboard vents?

If it’s the former, then maybe the blower motor is on the way out. Those can be a run one minute/dead the next type of thing and could explain why Goodyear said nothing was wrong.

it’s either the right temp, when blowing, or no air at all

Locate the blower for the heating and air conditioning. The next time there is no air, tap on the blower motor with a screwdriver or something similar. If it starts blowing air, you’ve found the problem. This happened to me with a Ford Aerostar. When the blower motor wouldn’t function, I could get it to work by opening and slamming the hood.

Yes, sounds like the blower motor is failing. Sometimes debris will get through the vents at the bottom of the windshield, go into the fan, and make it stick. You might be able to just figure out where the fan is, then clean the debris out, and make it work again. BTW: It’s a good idea to shop vac the vents under the windshield once in a while for this exact reason.