Just a tip most people probably already know. Took my '67 GMC 910 to the garage to have the charging system checked out. My voltmeter showed over 16 volts when the engine was running.
So, the mechanic ran the test, battery fine, starter fine, charging way too high. He thought the regulator might be bad. I looked up a new regulator (over $30), so, I took it home and took apart the regulator housing and everything inside is beautiful and clean which made me wonder. I got out the wire brush and cleaned up the bolt and the area where the bolt from the regulator attaches next the rad. Took the horn off and did the same thing to the bracket and bolt (it was acting up too). Lo and behold, the voltage is now 13-13.5 and the horn is loud and clear. This also eliminated the headlights flickering when driving down a bumpy road.
My windshield washer fluid bottle is cracked and drips. The regulator is right underneath. I think this is not the best place for the regulator!
Just some common sense but it took $20 to make me use it!