A high pitched whistle may be audible on some 1985 Calais models, primarily on medium to high blower speeds in the heater and defrost modes. The source of the whistle is from a small opening in the heater/evaporator case boss. This condition may be repaired by applying a small amount of medium bodied sealer to the boss attachment. See illustration. The boss is easily accessible without removal of any parts.
General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.