Probably a bad thermostat.
i have a 2001 celica and that happened to mine. there was an air block in the heating pipes and i took it to Toyota and they flushed it out and all is well now. yours mite a different problem but its worth checking it out. jamie
faulty control valve on heater or air in the lines
One reason is engine overheating - check your temp gauge and coolant as a first step.
It can, yes. The water pumps most critical function is to pumps water around the engine and control how heat is dispersed through the engine cooling system - keeping the engine from overheating. In most modern vehicles it also forces heated air to the heater core. If the heater is blowing cold air, it could be due the failure of the water pump.
One reason your home electric heater is blowing cold air is the heating elements are burned out. A bad thermostat may also be the problem.
Coolant level is probably low, Have it checked for an antifreeze leak.
most likely thermostat stuck less than $ 15 part
Low coolant?Bad thermostat?System airbound?Bad water pump?
sounds like the head gasket ...same thing just happened in my 97 cavalier
One possible reason for a vent blowing cold air when the heat is on could be a problem with the heating system, such as a malfunctioning thermostat, a clogged air filter, or a faulty heating element. It is recommended to have a professional HVAC technician inspect and repair the issue to ensure proper functioning of the heating system.
If the fan is moving and blowing cold air, your cold air intake is working properly. So long as your car isn't overheating it's a safe bet that the intake is functioning properly. Quite simply your temperature gauge will head straight for the red if the engine isn't getting cold air.