heater core possibly plugged and leaking
Probably - your head gasket is blown. Antifreeze will be coming out of the tail (exhaust) pipe.
No! 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.
The heater coil probably has a leak causing steam and vaporized antifreeze to be released into the vents. Is it using coolant?
heat core. leak. thermostat. no antifreeze.
Assuming that the blower motor isn't on fire, it's probably the heater core. Does the smmoke smell sweet. If yes that's antifreeze. The smoke does smell like anti-freeze. Does this suggest that the heater core is the problem?
Check Antifreeze level..make sure there are no leaks under the vehicle.
thermostst is stuck
Sounds like your heater core has a leak and the sweet smell is your coolant.
Most likely cause is low coolant. Check your antifreeze level.
I have a 02 buick rendezvous mine would blow a lil heat but never would get hot. We had it checked it was the thremostat, that is what was wrong with mine. They told me there is three things it could have been , it could be low on antifreeze , thremostat, or if you have to keep adding antifreeze often then it is your heater core.
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