If you plug in one wire from a winker base, the base is the ground, right? Right. So, if the wire is hot at the main harness, eliminate that test up to that connector. What is left is the wire to the end of the bulb socket. If that has integrity there, last thing that completes the circuit is the body of the winker, or the base, or what is considered a way of grounding the loop at the winker(s).
So, if this is a bad ground, you have two choices. One is, hide the arc if it happens, tag from under the base so the finish is not showing up top. Second objective so as not to arc at all is to have the pair of pliers already at a good known ground at the frame, then the other part of the adjustable pliers handle end, is to touch the body of the winker base. This completes the circuit, someone turns the key one. This should turn the bulb on or if it is on and won't wink, this is also how you make ground the better integrity; she starts winking again.
If you have a long piece of wire, cut back some so the strands are exposed. Touch the winker base to frame, turn key on, switch to failed winker side.
