if antifreez is blowing into cab, u need to replace the heater core the core has a hole in it. thses are not repairable and they are cheap to buy
Check Antifreeze level..make sure there are no leaks under the vehicle.
heater core possibly plugged and leaking
No! Thermostat.
The heater coil probably has a leak causing steam and vaporized antifreeze to be released into the vents. Is it using coolant?
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.
Probably - your head gasket is blown. Antifreeze will be coming out of the tail (exhaust) pipe.
May be a defective thermostat or heater core
heat core. leak. thermostat. no antifreeze.
if you have the heat on in any vehicle, and there is only cold air coming out of the vents (providing the engine coolant temp gauge shows that the engine is warm) then there is no antifreeze flowing through the heater core, this may be caused by a couple of things: first, there might be a leak in the heater core, but usually antifreeze will be leaking into the heater core housing and will be visible, or there might not be enough antifreeze in the vehicles's radiator, or the water pump might be damaged and not circulating coolant. hope this helps and good luck!
Most likely cause is low coolant. Check your antifreeze level.
Assuming you want it to blow hot, it could be low on coolant, a stuck open thermostat, a plugged heater core or a faulty temp blend door.
Ck the heater fan motor resistor .