I had to delete and redo becasue I always look at my GMC diagrams.
I don't have a 1963 Chevy truck wiring diagram, but generally......
1. There are no grounds running into the turn signal switch. Lamp grounds are handled by chassis metal "return" path.
2. The T/S switch is a "router" sending power to bulbs.
3. The T/S needs the brake lights run thru it so it can turn off the brake light signal to either left or right, so that the bulb blinks, because stop and turn use the same filament.
4. The turn indicator bulb is wired/"tapped off of"/"spliced into" the front left and right turn signal wires.
5. I see a white wire 17A, it is a power wire to output of brake switch.
Once these are double checked, let us know the problem. Don't count on the old harness being correct or the new harness being installed without a few errors.... and of course grounds are always a source of electrical troubles. Dozens of grounds needed by all bulb sockets, et al. Most grounds are "intimate contact connection". Just touching more or less. Some are bolted/screwed. Sometimes there is an actual ground wire. Maybe headlights, horn, dome, dash metal, tank sender...... As said, burned out bulbs will cause some weird issues.
The chassis and the body being most of the ground, as time passes,, corrosion, rust and fatigue sets in all over the place. Bad grounds are a headache to find/fix.
Last edited by bartamos; 08/01/2024 6:55 PM. Reason: puntuation and clarity
