Additional FWIW information. I watched closely when the four way flasher is on. It does cause the tach needle to fluctuate, but only a very little. The turn signal causes a major fluctuation, as does the cruise control (not realized before). The horn causes the needle to peg to the right. Also, when the engine is running at higher rpm, the turn signal bounce is not noticeable, but the horn and cruise control bounce is still very obvious.

I checked the battery voltage, engine off is 12.68 and engine running is 14.4, so it seems the battery is good and the alternator is functioning correctly.

I am going to clean the ends of all the fuses, but I don't hold out any hope for a change in the behavior; it just seems like a good maintenance chore.

If anybody has solved the horn to tachometer connection, I would appreciate any advice and or suggestions. (This is annoying me considerably!)

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