I had the same problem in my old 88 escort GT..
the electrical harness ford installed could not "Handle" the load and over time, began to fail.
I'm hoping your problem is just something in the multifunction switch (turn signal lever)
rather than needing a new harness like i did.
I'm out near Hopkins/minnetonka.

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2001 Ranger Edge 4x4 (sold)
2006 F150 Lariat 4x4 (sold)
2007 Explorer XLT (Destroyed by Deer on highway)
2014 Explorer XLT (inherited from parents)