Are you sure it isn't the hazard switch itself?

I was having a lot of weird bugs after installing a new one a couple months ago (the turn signals would blink a couple times then remain on without flashing). Those problems went away after a week and everything functioned fine until yesterday, when all of a sudden if I tried to use my turn signals both sides would flash at once!

I went to the shop today and got the hazard switch replaced and everything works great now...

I guess the moral of the story is a busted hazard switch can cause any number of bizarre problems, so don't ever discount it...

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'81 300TD Wagon 355k (Miss Diesel)
'83 300SD 180k
'84 500SEL 190k (Parting it out)