[hoondogg]

1978 Formula. Tach is not working. On the coil, there is batt and tach. Should there be 12volts on both terminals when the key is on and engine is off? I have power on both tach wires at the tach when engine is off and key is on.
Thanks

[Trevor78]

Standard, the engine isn't running so gauge shows that even with power there. A 78 tacho should hang down when off and not return to 0, except when powered up. If needle doesn't twitch, then there's nothing going on there. The tachos also commonly failed 45 years on, expensive and flimsy to repair only to fail again. At least there's a reproduction now available, at least for some years.

[DanC]

Not mine! I've seen this on eBay https://www.ebay.com/itm/142558219997

DanC

[Trevor78]

The years are wrong. 79-81 quartz clock type.

[bhill86]

Thought there were late 78 versions that didn’t say quarts above the clock and yet had the new tach and clock mechanism inside.

[Trevor78]

Not sure exactly when the changeover was, if 1st 79 model or gradual late 78 model etc. Point is you need to know what tacho you have and that this type only fits the Quartz clock version. Different tach internals and operation, different clock, different gauge rear shape. This version not done repro so the circuit board can be a handy part to have. The early models didn't say Quartz even though just swapped to it, but could be identified anyway as the tacho needle returned to 0 when off, not hang down.

[bhill86]

Agreed

[Trevor78]

For sake of adding detail pics... thanks Tom, saved me uploading.


Non-Quartz clock and tacho version....round rear body and small round circuit board.

http://www.thepartguy.com/images/pro...Qtz)tach-4.JPG

http://www.thepartguy.com/images/pro...Qtz)tach-3.JPG



Quartz clock and tacho version, even without Quartz text on face.... plastic rear body with flat sides, large half moon circuit board almost same size as gauge body.

http://www.thepartguy.com/images/pro...-81)Tach-3.JPG

http://www.thepartguy.com/images/pro...-81)Tach-4.JPG