I was adjusting the rack & pinion adjustement, and when I got done both the horn and tach had quit working. Thinking that I must have tugged on some wire by mistake, I went back and looked for the loose or hanging culprit. But all I found were vaccume lines. Checked the fuse box and all the fuses looked intact, but I gave them all a good twist just in case. I've read all about the cigarette butt trick, but haven't tried it as I just wasn't sure. Why would the tach amp affect the horn? Is there a common ground for both the tach and horn?

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'83 300D (220000 miles and counting)

Since the tach sensor is on the front of the block and the horn is up there as well I believe? You might have disturbed a wiring harness perhaps. Are you reffering to a 123 though as you mention rack and pinion? If another car especially gas I would not imagine a simular senario as they do not use crank sensors for their tachs I believe but I am possibly wrong.

Check the fuse again. You blew a 10A. Happens to me from time to time. Horn and tach are on the same circuit.

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91 350SD
14 F150 Eco
19 Fusion Hybrid
11 GT500

redassag00
You were right, thanks.
You could not tell it was blown untill you got you nose right on it. Replaced it and both the horn & tach work again.
Thanks

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'83 300D (220000 miles and counting)

Glad to hear it The have hairline 'blows' in the fuse.

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91 350SD
14 F150 Eco
19 Fusion Hybrid
11 GT500