Yep I agree with both of you on the heat issue and the capacitor. I have a replacement on the way.. When I get that and install it I'll pull the other and diagnosis it and check the capacitor... Does anyone know what size capacitor it would need..

Thanks

Capacitors go bad in the tachs like they do in the small clocks, you could try replacing them.
Dan

I put a *small* tach in my '84 (no issues other than having to run a direct wire through the firewall from the coil to the tach -- there was no OEM wire to use that I could find, like in my '93). Is your tach a small one like I put in my 84, or is yours the *large* kind that replaces the clock (and like I put in my '93)? And did you have to run your own wire, too, or did you find the OEM tach wire that I couldn't find?

Anyway, there's nothing in the wiring that should cause the tach to fail after 10 minutes, unless you're talking about the 2" tach and you cobbled together a new power cable for it. Assuming, instead, that you have the *large* type, if you never had any problem with the clock you swapped out, there shouldn't be any issue with a power supply via the instrument panel's circuit board, as the old clock and your new tach would share the same circuitry -- only the tach feed is new (i.e., wasn't in the clock).

Therefore, regardless of which size tach you're writing about, I'd suspect that some electronic element in the tach is gradually overheating and causing the tach to fail.