Ok, I'm lost. I've gone through 4 large tachs and none of them work? Possible but I figure it's gotta be me. Here's the deal. I pull out the clock on my 89/240 and replace it with a large tach (followed Barton's instructions. Easy as pie. Use the red/white wire and everything) and the tach does nothing. Went through this with 4 different tachs and not a blip out of any of them. So I went under the hood and can see the other end of the red/white wire on the negative side of the coil, so thumbs up there. Now the clumsy part. The only way I could think of to test them was to put an alligator clip on the (-) terminal of the coil and clip the other end to the male post where the red/white wire goes. Still nothing. So my question is, am I doing it right? There's gotta be something I'm missing. Any ideas?