Intermitent Tachometer

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Jul 1, 2021 | 04:35 PM

Jim4924

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Joined: Sep 2007

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From: Ashville, New York

Intermitent Tachometer

My tach doesn't start working until I'm 5-6 miles down the road. It seems to start working when the motor is warmed up. I realize its electronic, not vacuum or anything else. Does anyone have any suggestions of what the problem is?

Thanks,
Jim

Jul 1, 2021 | 06:00 PM

BKarol

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From: Northeast

Bypass the tach filter. Run the tach wire directly into the distributor. At least eliminate this first as being the problem and the easiest.

Jul 4, 2021 | 02:48 PM

bschuus

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From: New Jersey

Mine does the same thing from time to time. I will also remove the tach filter for a try

Jul 5, 2021 | 03:18 PM

Jim4924

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From: Ashville, New York

I'll try that, Thanks!

Jul 6, 2021 | 01:16 AM

7T1vette

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From: Crossville TN

Might also be a foil 'fracture' on the circuit board which 'makes' or 'breaks' as temperature changes.

Jul 6, 2021 | 02:24 AM

doorgunner

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I saw an article about the Ignition module in HEI Distributors causing irregular tach readings when it gets too hot. (?)

Jul 6, 2021 | 07:51 AM

interpon

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From: Indiana

I am betting board bad.. i read a lot of articles and advice , although a great test to remove filter..it seems to always see board issue..

Last edited by interpon; Jul 7, 2021 at 09:59 AM.

Jul 6, 2021 | 08:54 PM

7T1vette

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From: Crossville TN

But if it reads correctly some of the time, it's not a defective component. If so, it would not read at all or not read correctly when it was operating. That's why I think it is a simple continuity break somewhere in the system: 1) a fatigue crack thru a single foil trace on the tach circuit board; 2) an intermittent tach filter; 3) tach signal wire with a break in the run or a bad connection at a terminal; etc, etc. I'm just suggesting that you try to identify simple fixes before you dump ca$h at the problem.
Good luck.