DEAR MR.{S} WAS COMING A MINE SHOP A MERCURY GRAND MARQUIS 1988 AND THIS CAR HAVE LOSSE FLOW AIR FRONT THE FRONT TO DEFROSTER, ALSO FIRST CHANGE THE TEMPETURE AFTER THAT CHANGE THE AIR FLOW. I'M DID CHECK THE VACCUM IN DASH { I'M WAS REMPLACED HEATER MOTOR, SP... Login to read more.