Burn some of the plastic where nobody can see it with a lighter. If it is the same smell, I think your jet is on it's way out by melting it's way through the plastic housing. But never heard of it. Also I believe they should only be heated if the outside temperature is below a certain temperature. Maybe it's now heated all the time if sensor or so sends wrong signal. Does your outside temperature reading on the OBC work correctly? Regards Ralf