Join Date: Feb 2009
Location: Glendale, Arizona, USA
Model: 1987 GL1200 Interstate 280,000 miles
All those extras, lights, cruise, airhorns and such are usually the source of your kind of problems. The horn and turn signals are on the same circuit as the brake lights, and the cruise is hooked into that circuit. Look just ahead of the gas cap for the rear brake light wires. The Markland cruise hooked into those wires.
If it were me I'd take the bike back to stock and get it working right, then reinstall any functional stuff I thought it needed.
Why ain't we ridin'?