The 1989 and early 1990 F cars may have a "tapping" type noise coming from the rear hatch area. This noise will be worse on rough roads. The noise is coming from the contact assembly in the hatch lid, which is used to supply power to the rear window defogger.
The moveable terminals in the contact assembly if too long, may hit the plastic body of the contact assembly when going over bumps.
A new part was used in production beginning with the following VIN: LL122492
Replace the contact assembly in the hatch with new part number 10098526, following instructions in the Service Manual.
Part is currently available from GMSPO.
Labor Operation Number: N3024
Labor Time: .3 Hour
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.