Why is there a gas smell inside the car when starting car in A/C heater on?

I think what you are smelling is a coolant leak, because you mention the word "sweet" and heater "ON". Gasoline NEVER has a sweet smell but antifreeze ALWAYS has a sweet smell/taste and that is why animals drink it and die. Check your passenger floor for tell tale signs of coolant leaking from the heater core.

Take care right away. if it is a coolant leak you dont want to overheat if it gets worse, but if it was that is would get worse as you warm up so i believe it is a fuel leak but from a injector. when air is pulled from outside it brings the fumes that accumulates from higher fuel pressure in fuel lines when car is stopped. it wont do this as much while you drive so it goes away. just a thought.

It might be your evaporator core, I had the same problem on my 2006 Nissan Altima 198,000 miles 2.5L, and my mechanic said it the evaporator core and that is why my ac isn't working. I still did not change out the evaporator core so I am not sure but ask a couple of mechanics to make sure. When the mechanic adds the freon for the AC it leaks out of the AC vents and you can actually smell it.

wht does my car smell like gas when i make aturn left or right

I have a 2011 altima and when the ac is on i dont smell anything but when the heat is on it smells like gas... anyone know what this means

I have a 2005 Nissan Altima and just recently started smelling gas when i turn my heater on or a/c on and that was after i changed the spark plugs

I have a 2006 Nissan Altima 2.5 liter can having a very bad smell like antifreeze in my car don't know what it is