The Pontiac Bonneville has been in production since 1957 with updates and changes made every few years. With cars dating back to the 1950s, it's no surprise that many of them are ready for a new stereo. Upgrading the stereo in the Bonneville is a straightforward project and takes about an hour to do.
Disconnect the negative battery cable from under the hood. Secure the battery so it doesn't contact any metal parts.
Slide a finger under the trim above the stereo and loosen the clips, continuing under the steering wheel. Remove the trim and set it out of the way.
Locate the three screws surrounding the stereo in the Pontiac Bonneville dash and remove them. Pull the head unit out of the dash and disconnect the wires from behind the stereo.
Secure the new stereo into the GM radio adaptor kit. Connect the wiring harness adaptor to the original harness and then into the back of the new stereo. Connect the antenna wire; models after 1988 require an antenna adaptor that slips over the manufacturer's wire.
Push the entire assembly into the dash and secure it with the three original screws. Reconnect the negative battery cable and turn the radio on. Test the speakers and radio controls to ensure they are working properly. Snap the trim back into place on the dash.
