I agree that the turn signal switches that have only two rivets go bad to often. When I go yard picking I try to get the older ones made by SFK, if I remember correctly. They have four rivets and they are the only ones I have seen that put their name or initials on them. That is usually a good sign!

I would also be suspect of the headlight dipper relay out on the drivers side fender. It is silver oblong shaped box with two connectors that plug onto it. You should hear a click out there when it works the low to high and back again. It holds the high lights on after you let go, if it flips or possibly the turn signal holds it over there?
I have not had a reason to played with them to really know. That is why I sided with a bad turn signal switch too!

It is very easily to find the terminals to be corroded on the device. Or sometimes they can get stuck or sticky internally and not work. It has a mechanical lever action that flips back and forth. The box can be uncrimped for a peek inside if necessary.

Good luck either way!

Phil