First check the water level. If the water level is low or very low, you may have air in the radiator. If you have a small leak, you will have enough water to cool the engine but not enough to heat the heater core. Adding water to the radiator may not be enough. Air in the heater core equals no hot air in the cabin. This problem is so bad in some engine configurations that some cars go as far as to actually have a 'bleeder' at the front of the engine, by the upper radiator hose/thermostat housing (Dodge, BMW, etc.). The heat selector lever/ switch in the cabin may be defective (electrical) and may not open the hot water valve enough, or even be disconnected (mechanical). Some (Ford and foreign cars) use vacuum to operate the valve and those lines may be cracked, worn, pinched or just leaking. You could also have a clogged heater core. These are 3 possible items you could start with, in that order. The thermostat could be At Fault, but this is a give away. If the thermostat is stuck open or missing and you drive the car for a distance, the engine will take a while to warm up then overheat, and the cabin heat will follow the engine temperature. If the engine overheats, you need to take care of that motor more than worry about the heat in the cabin. As you said, you're not asking what to do with your overheating car. You would have taken care of that motor by now and taken care of your heater problem with it.
if the heater does not blow out warm air change the setting.
heater on at idle and will not blow warm air. when moving it blows the warm air from the vents. what will cause this
Isn't a heater supposed to blow warm air?
It could be the thermostat on the engine. If the engine does not warm up adequately the heater will never blow hot air.
engine not warm, low coolant, or stuck thermostat
Low on coolant. Stuck open thermostat. Poor circulation (plugged heater core).
Faulty thermostat. Plugged heater core. Temp blend door malfunction.
Your thermostat is most likely bad. It controls the flow of warm water into your heater core which warms your air. Its a common problem in winter and an easy fix.
Poor coolant circulation from a plugged up heater core. Try flushing the heater core and replacing the thermostat.
Probably need to add antifreeze. Check the Radiator not the overflow tank. If you are low on antifreeze it will not circulate through the heater core.
it is a heater. heat. it blows heat. warm air
Any heater that only blows luke warm air isn't getting warm or hot water to the coil. This sounds like a problem with the thermostat not closing, and allowing the engine to heat the water properly for the heater.
Heater core may be plugged . Flush the cooling system, also check thermostat.
It could be that you need coolant or it's low.
your heater core hoses could be plugged up and not letting much hot anti-freeze into the heater core then when you try to blow alot of air through it it cools the warm air off too much and you get not so warm air. try a cooling sytem flush
Check your anti-freeze levels
The front expansion valve is clogged.
It doesn't really blow it out it just warms the cold air.
why does ac blow warm air? why does ac blow warm air?
Check your coolant level. If its too low the sensor won't read the temperature of your coolant.
it's because of heat transfer into convection .
heater core possibly plugged and leaking
The heater does not blow air because it emits infrared rays that have heat molecules within them, thus releasing heat, not blowing it. A heater does not blow air becasue there is no moving air source within the heater. The heater emits infrered rays that cause heat to slowly flow out of the heater.
dual control damper needs replaced how do you change it