You may be low on coolant, or the thermostat is stuck open, or the heater core is plugged up, or the temp blend door is broken.
You are likely in an antarctic region.
You probably have a bad thermostat.
I assume your car heater is blowing cold air, when the heater is on. It seems that, you have air on your coolant. that air pockets blocks the cooland to travel through your heater. it may be a sign of a bigger problem such as blown head gasket in the old cars, such acura legend
Get the air out of your heater core.
the heater blows warm air when fan is on low but blows cold air when fan is turn to higher setting
An automobile's heater that blows only cold air could either be a faulty thermostat or, more likely, a faulty heater core. A trip to a mechanic or shop that specializes in radiator and cooling system repair should be able to diagnose and repair any problems.
heater hoses might have been disconected
The most common reason a automobile heater blows cold air is the water level is low. Check the water level and fill to the appropriate level.
we changed radaitor & thermastate , now heater blows cold air
ihave a 1986 chevette that when i turn defrost on it blows out heat and when i put heater on it blows out only cold air? ihave a 1986 chevette that when i turn defrost on it blows out heat and when i put heater on it blows out only cold air?
you must have low coolant or a bad heater core
The heater may not be on - but the fan still blows air through the vents when they're open !