I've read many times that replacing the tach's circuit board will solve many tach-related issues.  Well I have the dash partially apart (enough to get to the speedo cable which I've already replaced) and I'm trying to decide if I should replace the board.  Sometimes my tach works perfectly normal, but other times it seems to get "stuck" at a lower RPM than what the engine is running at, or it will jump around.  Are these issues indicative of a faulty board or is it just time to rebuild the whole thing?  

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On my 79, I was able to remove the lens and bezel from the front (I think I lowered the steering column) and was able to remove a few screws and the tach pulls right out from the front. The tach board is held in place with 3 speed nuts - very easy to replace. The tach then just pushes back into the harness through the dash (also very easy) and reverse the rest of the process. My tach was doing things similar to yours and the new board resolved the problem... Paul

Take a look at this info You may need to do a zero adjust

Thanks for the info, guys.  I think the 78-82 folks are pretty lucky in this case.  The tach does not pull out from the front on the older cars.  I took the entire main gauge cluster out tonight - whew!  stressful cause you don't want to break anything and the whole time you're wondering if this will ever go back together.  Once it's out, though, it doesn't seem like it will be too bad.  Bob, that link is interesting and helpful, but it's for '78 - '82.  I wonder how much is applicable for the older cars.  I think I am going to order the board from that company, though.    

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It looks like the willcox tach board has an zero adjustment, the instructions for the Midamerica has you turn the key on and if not at zero remove tach needle and reinstall it. something to look into to make sure

Bob - yep, I agree that the Wilcox one has a zeroing adjustment.  Just hoping it can be calibrated without a running engine and by just applying a voltage to it.  

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