76al

When i took the tach wire from fire wall out of plug (No Filter) and put it into The Dist cap,The tach works got a new tach filter wired up then put into filter nothing ,Put wire back into cap works but when you shut car off tach does not go to zero but if you turn key on no start goes to zero confused Do i need Filter thanks Help

'75

When the key is off, the tach needle can settle anywhere, but goes to zero with key on. Seems like there is something wrong with the new filter, you should see no difference when it's inline but it protects the tach from hi voltage spikes.

0Willcox Corvette

Original tachometer boards and our reproduction are made to hold the last signal received. So if you are idling at 700 when you turn off the key the tach should hold it pretty close. (aprox.. they still will drop depending on the condition of the analog movement). China made boards won't do this nor will the reproduction china tachometers.

76al

Just got new filter how can I check see if good thanks

76al

Original tach in car

0Willcox Corvette

If the tach works without it, plug up the filter and see if it works with it. You won't have what it takes to check the filter.

Willcox

76al

The tach did not work with the filter only without and the tach is steady when working what else could it be looked at what is intailed to take tach out ,not looking forward to that the new filter read 15.5 ohms old filter 16.5 ohms thanks for your wisdom and help al

JimLentz

Do you mean Kohms? 15.5 or 16.5 ohms sounds way too low. I assume you measured that from input to output, is that correct?

76al

Yes input to output on my multi meter measured at the 20 ohms thanks

JimLentz

Based on the schematic in this thread it should read around 15.6 Kohms.

76al

Can I run without tach filter ,when I did the tach worked normal no fluctuations ,not looking forward to taking out gauge cluster if it is the tach board thanks for your help

JimLentz

Yes, you can run the tach without the filter. Changing the tach board is a pain.