We are trying to figure out why the glass on our stove is covered with soot. What can be the causes? We have had the stove 3 yrs, last yr the problem started, we were told to run our fan over the air intake . Seemed to work. But now the problem has started again. Last night we took apart the stove and vacumed to make sure all was clean, washed the glass. This morning it has soot on it again. Thank you for any help.