Q: After a few minutes of turning on my heater an odor emits in my car. The windshield also appears to have a residue on the inside. What could be causing this?
A: The heater core may have a small leak. The heater core is a like a small radiator, commonly between the engine and passenger cabin. The heater core radiates thermal energy in the heating/air conditioning ducts of the car. Antifreeze flows through the heater core. When the blower fan is turned on, if the heater core is leaking, it will emit an antifreeze smell in the car. It could also be blowing some of that moisture onto your windshield. Check the floorboards for moisture and the antifreeze level in the coolant expansion tank. Only check the antifreeze when the engine is cold. A small leak in the heater core can emit a big odor.