if you have air off and the have the air recirculate to have outside air come in then yes you will get hot air blow in if its warm or hot outside
My car is stuck in fresh air mode because the previous owner improperly replaced the cabin air filter and broke the servo arm. When i have the AC off, sometimes I get that hot air flowing in. I just turn the AC on, turn down the temperature, then turn it off. No more hot air.
Mines only get hot at top speed otherwise it don't so i don't think it has anything to do with the AC and that's when my heat and everything is turned off, it might be from the ingine and all the work its doing + I live in NY so I brake a lot so I think that can cause it as well
even if the fan is off and you have it in fresh air/ mode, the heat coils still get warm and will make the cabin warm. The heating system needs to prepare for that moment you DO decide to turn on the heat to have instant warm air. If you turn down the temperature, it doesn't get warm when on fresh air. I think this applies to MOST cars because every car i had was like that. If the temp was still on 80 but the fan is off, when in fresh air mode it will still get warm. Turn the temperature down it will be cool fresh air