It's all a question of names,
air conditioning takes air, passes it over a cooling matrix which, cools and drys it (hence the water you get dripping from under your car)
the heater takes air passes it over a heating matrix and heats it up.
A car with the air-con on on a cold day cools and dries the air first then heats it up, and passes the warm dry air into the cabin. On a hot day dry chilled air is provided as the heating matrix is bypassed.
Without air con you're only heating up damp air, which can cause condensation, or on a warm day, provide air at ambient temperature.
...if wishes were fishes, we'd all cast nets...