Tachometer Repair

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Nov 12, 2018 | 05:20 PM

CorvetteRules

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Drifting

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From: Mays Landing, NJ

Tachometer Repair

When I bought my 1991 Coupe I knew the tach didn't work, but since it's an auto trans wasn't important to me. I have become curious as to what could be the cause of it not working. Several threads that I have read here talk about a bad tach filter or a resister on the circuit board going bad. While I already have a list of improvements I'd like to do, at some point in the future it will be something I'll probably like to fix. Anyone have any experience with this?

Nov 12, 2018 | 05:29 PM

WVZR-1

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Quote:

Originally Posted by CorvetteRules

KEY-ON (not running) does it park @ 0? EXACTLY? If not where does it park? Get a hand held and check @ the distributor. Does the car have C68 AC? If it has C68 ,the AC control can be used to confirm RPM.

Most everyone with a '90 - '91 has had this experience

Last edited by WVZR-1; Nov 12, 2018 at 05:30 PM.

Nov 12, 2018 | 06:28 PM

bosshog8

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From: Pine Barrens New Jersey

http://batee.com/corvette/dcrg/9096_analog_ic/

Nov 12, 2018 | 07:18 PM

CorvetteRules

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From: Mays Landing, NJ

Quote:

Originally Posted by WVZR-1

Before I turn the key on the needle is at the bottom, but I never looked to see if it was at 0. I do notice that as I accelerate the needle pegs above 6000. On my next drive I will pay better attention. The car does have C68, how can it be used to confirm RPM?

Nov 12, 2018 | 08:06 PM

WVZR-1

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Quote:

Originally Posted by CorvetteRules

If the needle moves when running but doesn't park @ 0 with just KEY ON then I believe you have a calibration issue. A filter issue generally the tach either works or doesn't -seldom I believe it's erratic BUT if it always goes past 6K. maybe you do have a filter issue. I've never had a filter issue. Cars I've seen with an issue generally the lead had been pulled from the body or a bad connector @ the distributor.

***don't worry about where it parks with KEY OFF (It can be anywhere)

C68 - push FAN + and FAN - simultaniosly for a few seconds and display should show 00 I believe, push AUTO FAN and it should display C68 codes. After code display if you use FAN + or - various paramaters are available. Toggle to 6 I believe and hit AUTO FAN - RPM will be the display /25. If I get a chance I'll copy the entire list of values. Do you have the FSM?