First thing to inspect is that there is enough anti-freeze / coolant.
If the coolant level is full, then this sounds like a symptom of a failed water pump.
Although the pump may not be leaking, the impeller may not be spinning and moving the coolant through the engine.
why doesnt my heater work on my1985 BMW
probably the heater core is clogged
it has a partially clogged heater core.replace the heater core
Plugged heater core. Try flushing it.
Low on coolant. Bad thermostat. Plugged heater core. Temp blend door inop.
Blows cold air through the heater. Overheats. Bubbles/oil in radiator. Check spark plugs for condensation on plug tips.
if it doesn't heat your heater core is most likely clogged and if it doesn't blow at all then the blower is messed up.
The problem of a vaguely worded question....See "Related Questions" below for a range of possible relevant responses
Check the heater core; either it or the lines running to it are clogged.
You can blow a head gasket or the head can crack or be warped.
heater will not blow on a 1996 ford contour
if the heater does not blow out warm air change the setting.