Some 1985-1986 C/K and 1987 R/V models may experience a whistling sound at or near the front door glass beltline seal. This sound is due to the window regulator mechanism moving the window away from the beltline seal while in the full up position. The whistling sound may be more pronounced when the A/C control is in the "vent" made and the blower fan is on medium or high speed.
To repair this condition, a new inner beltline door seal, P/N 15569071 (L) and P/N 15569072 (R) has been released for service. This new seal is approximately 3/16 of an inch longer than the original seal. Measurements showing the difference between the old and new seal are shown in Figure No. 1.
The following VIN breakpoints identify when the the new seal was incorporated into production.
St. Louis Chevrolet HS154946 GMC HS519882
Flint (Pickup) Chevrolet HF390307 GMC HF724416
Flint (Suburban/Blazer) Chevrolet HF152540 GMC HF523110
Janesville Chevrolet HJI45686 GMC HJ517885
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.