Starting with the following VINs, 1989 R/V production began using electronically tuned AM radios (ETR):
GMC: 1GTER16K4KF520461 1GTHV33N7KJ509268
Chevrolet: 1GNEV18K3KF150932 1GBGR34K9KJ121659
The AM ETR radios have a balance feature which allows for sound adjustment from the right to left. 1989 RN models equipped with AM ETR radios have just one central speaker. The balance knob should therefore be set on center or left of center for radio transmission through the speaker. Do not attempt to repair a 1989 RN AM ETR radio with no radio transmission when the balance knob is set right of center.
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.