There's a malfunction somewhere. You need to have a shop perform a system performance test in order to properly diagnose the problem.
Actually, the AC is always blowing cold air. Its just that sometimes your nerves can't feel it because your body is used to it.
Well the main reason why your car blows out cold then hot is because the air conditioner may not be working properly. You should go to the car shop and get it fixed.
The Air Conditioner is on
it could be the heater core and ac housing unit that allows hot air to be mixed with the cold air or it could just cancel out the cold due to the motion of the car
Try your thermostat
If the AC is on Vent and it blows hot air in and the temp is at coolest. I think it does not matter because when you have it in vent it is venting air from the out side, it will start blowing air from the out side meaning if its hot out side the air will come out hot. Sometimes a car might blow hot air when you have it on full AC and cooldest. When you accelerate your car hard but it should cool down after you stop accelerating hard.
Blows hot or cold air (as selected) through the ductwork behind the dash.
A car heater taps off engine heat. If you aren't driving, then the engine is cold and there's no heat for the car heater to use.
get a new car. or better a new air con stupid
Only blows cold air with the a/c on while driving, your cooling fan or fan clutch is bad depending on the year, make and model.......... Only blows cold air with the heater on while driving, you will have a bad or broken internal a/c - heater control door.....
Sounds like it is low on coolant.
Check to see if your condenser fan is running when a/c compressor kick on.