Low coolant, failed thermostat, partially plugged heater core...............
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.....
Poor circulation probably due to a restricted (plugged up) heater core.
Low on coolant. Stuck open thermostat. Poor circulation (plugged heater core).
It is either your water pump or your thermostat
Well it should blow cold while driving and stopped. You probably need to get your AC recharged. Hope I helped!!
Your heater will blow cold air only.
thermostat probably damaged or stuck....and worse case scenario....your heater core is going out.
It doesn't really blow it out it just warms the cold air.
it wont blow heat itll blow cold air
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.
it has to heat up, just like water has to warm in the faucet.