Check under the hood for an obvious fuel leak. You might an injector leaking.
Leaking heater core.Leaking heater core.
Blown Heater Core - The heater fan blows past the heater core and if it has a hole in it your antifreeze ios being blown onto your windshield.
heater core
It's leaking somewhere, possibly in your heater core.
More than likely the heater core is leaking.
Antifreeze will be leaking in the floorboard on the passenger side, there will be a smell of antifreeze through the vents.
If it's a sweet smell then its probably a heater core leaking antifreeze.
The possible explanation for the smell may be that the heater core in the vehicle has a slight leak, therefore the smell of evaporating antifreeze will come through the vents until it is all dried up. Solution is to take the car to a garage and get the heater core replaced.
Chances are it is a busted heater core. It your window has a fog on it when you turn on the ac or heater.
Check for a line leak to your heater core or a leak in the heater core it self. Usually it is under the dash on passinger side.
A bad smell coming from the heater in a vehicle can indicate a bad heater core. One way to check this out is to see if the smell is worse when you sit in the passenger seat. If it is, there is a good chance the heater core is bad.
Generally, with that smell- the heater core has gone bad.