Hello all,

I was hoping to get the lists experience base on a broken Smith tachometer in my 67' P1800. Is their a common failure mode for these tachs and if so, is there a fix? I just repaired my speedometer, but I'm a bit reluctant to jump right in to the tach, since I suspect it is a electrical, and not a mechanical, tach. Is this something I should send to a specialist?

Your comments welcome...

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

Good Hunting

Does it work at all??? IF not, you might get lucky just beating on it a bit... mine gets caught up every now and then, and a quick blow to the side with my hand usually wakes it up...

If not though, heck...if you've fixed your speedo, you coudl probably fix the tach. If it ain't the wiring, its probably just stiff... just a guess though.

-Matt

If it used to work, the wiring is probably not suspect. One failure mode I know of is that there is a calibration pot, and after 36 years of not being adjusted, the connection between wiper and windings corrodes. The fix is to exercise the pot and then recalibrate. In my case, the car is modified anyway, so I just replaced it with an Autometer Monster tach -- fits right in with minimal grinding of the dash material. You could put the original back in and no one would know anything had been modified.

How did you fix your speedo? The problems I've had is with the worm gear slipping forward an causing the spinning magnet thingy to contact the pickup. Easy enough to put it back where it should be, but I've never managed to make it stay there. ???