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Tachometer Question

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Old May 31, 2016 | 10:56 PM
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Hello All!

Recently purchased a 1980 Corvette and Tach was working fine. Tach becomes active when car is started and responds to engine revving; however, the tach appears to be reading 1400 rpm higher than normal. It idles showing 2200 rpm. This started shortly after I changed the thermostat, but this should be irrelevant. Any thoughts or recommendations? Thanks!
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Old Jun 1, 2016 | 07:24 AM
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Needle on tach SHOULD go to ZERO when ignition switch it turned to ON position, without engine running....if it's not, then you'll hafta pull the cover off & pull the needle straight out....carefully, and set it to read ZERO. If it doesn't react good after that, then you'll prolly hafta change the filter on the distributor, and/or install a new circuit board on the tach.....I did both, got from Willcox. Unless the '80 is a different setup than my '79.....(My tach was stuck on 4,000 rpm, so I HADTA do this to make it work!)
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Old Jun 1, 2016 | 08:29 AM
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Originally Posted by Sluefoot
Needle on tach SHOULD go to ZERO when ignition switch it turned to ON position, without engine running....if it's not, then you'll hafta pull the cover off & pull the needle straight out....carefully, and set it to read ZERO. If it doesn't react good after that, then you'll prolly hafta change the filter on the distributor, and/or install a new circuit board on the tach.....I did both, got from Willcox. Unless the '80 is a different setup than my '79.....(My tach was stuck on 4,000 rpm, so I HADTA do this to make it work!)
Thank you for the response I will give this a shot!
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Old Jun 1, 2016 | 11:09 PM
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Originally Posted by Vettez7
Hello All!

Recently purchased a 1980 Corvette and Tach was working fine. Tach becomes active when car is started and responds to engine revving; however, the tach appears to be reading 1400 rpm higher than normal. It idles showing 2200 rpm. This started shortly after I changed the thermostat, but this should be irrelevant. Any thoughts or recommendations? Thanks!
It is not relevant to the thermostat change.. Like mentioned above, when the key is turned on the tach should go to zero... Does it do this?

More than likely you need a tach board.... https://willcoxcorvette.com/corvette...80-82-usa-made

Willcox
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Old Jun 2, 2016 | 08:35 PM
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Originally Posted by Willcox Corvette
It is not relevant to the thermostat change.. Like mentioned above, when the key is turned on the tach should go to zero... Does it do this?

More than likely you need a tach board.... https://willcoxcorvette.com/corvette...80-82-usa-made

Willcox
Thank you for the reply. I checked it out just recently and when I turn the key it does not go to zero. When the key is on the tach shows 1600.
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Old Jun 3, 2016 | 04:45 AM
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Most likely a problem with the electronic circuit board. But, it wouldn't hurt to replace the tach filter can while you're at it.
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Old Jun 3, 2016 | 01:36 PM
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Originally Posted by Vettez7
Thank you for the reply. I checked it out just recently and when I turn the key it does not go to zero. When the key is on the tach shows 1600.
If the tach is not responding with the key on I'd remove the tach and before I purchased a board I'd test the retaining clips inside the housing to see if you had power and ground there. If you do then replace the board for sure.

Here is how you get the tach out of the car with ease.
1978-1982 Corvette Tachometer Testing, Removal, Board Installation



Willcox
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