1800;

If the tach essentially works but is "generous", its likely the cal pot*. If its totally dead, try a tap or two to awaken it...if that doesn't help, double check wiring...check the easy stuff first...is there power?...is there a loop of the points line at the tach pick-up?...I have a wiring diagram of the what I understand was the standard circuit used in Smiths tachs, as fitted to a number of vehicles (not confirmed yet if it also applies to 1800 tachs)...I will post this on Service Notes Page of you like, and are comfortable enough to dive into the circuit...its not too complicated, but beware, I'm not certain, but I would bet a hot-fudge-sundae that all of the transistors are Germanium types which cannot be replaced by silicon types.

*see additional notes at: http://www.intelab.com/swem/service%20notes.htm#Gauges

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