Factory Tach problem
Thread Starter
Le Mans Master
Joined: Oct 2005
Posts: 6,247
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From: Glen Allen, VA
Factory Tach problem
My tach reads significantly higher than it should. I checked and for instance at an indicated 3200 rpm, it's actually turning 2600. I sent the tach board off to board member ACECO a couple of years ago for the same problem and he fixed it, but now it's doing it again. Has anyone had the same problem and what did you do to fix it? I'm considering a buying a new tach board, but would like to know if anyone has fixed the same problem with a new board? My car has never had a tach filter and it still doesn't. Could that be what's causing the problem? Mine is a 79 BTW. ACECO, this was not meant to be a slam against your work at all, sorry if it was taken wrong by anyone. See my post below.
Last edited by C3 4ME; Mar 10, 2010 at 06:52 PM. Reason: clarifying what might have caused a problem
Team Owner
Joined: Jun 2000
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From: Southbound
Cruise-In II Veteran
Don't you have to zero the tach after replacing the board? Tom Russo had an article in Corvette Enthusiast a couple or three issues back about tachs, tach boards, and zeroing them.
Thread Starter
Le Mans Master
Joined: Oct 2005
Posts: 6,247
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From: Glen Allen, VA
I don't know about replacing the board whether that required zeroing or not, as I haven't replaced my board yet. I do know after the existing board was repaired it was reading dead right, and now it doesn't anymore.
Thread Starter
Le Mans Master
Joined: Oct 2005
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From: Glen Allen, VA
So 78 Pace, you got your board from Willcox? You zero'd it out, and it's still not reading right? Was it ever reading right after installation that you know of? I ask becuase buying a tach board from Willcox is exactly what I was thinking of doing.
Team Owner
Joined: Jan 2006
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From: Crossville TN
Your tach filter has crapped out. Since it works, the tach board is probably OK. But, it is picking up 'spurious signals' and counting them as engine rotations.....bad tach filter. Eckler's sells them: $43 for original style, $30 for a substitute piece.
Thread Starter
Le Mans Master
Joined: Oct 2005
Posts: 6,247
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From: Glen Allen, VA
Guys, it was pointed out to me that my original post my be taken as a slam against ACECO and his work. That is absolutely not my intent. He is a very stand up guy, and even repaired my tach and sent it back to me before I got my payment to him. I'm sure the problem I am having is becuase of something with my car, maybe as 7T1 suggested above, I need a tach filter, not becuase of ACECO's work. ACECO, if you read this, my apologies if my original post offended you.
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Safety Car
Joined: Jun 2004
Posts: 4,374
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From: Beecher Illinois
I'd say the board went bad again, possibly because of the lack of the filter.
I've already replaced 2 of mine. One on my 25 mile Pace Car
Aceco was nice enough to check my old ones but both needed an obsolete part.
As for zeroing them out, mine were simply a matter of having the ignition switch 'on' and pulling the needle off and reinstalling at 'zero'.
Be carefull with the needle, they're fragile. Don't ask how I know
If you'd like to 'borrow' a new board to check things out, I got a spare one(always prepared!)
Try it, if it works either leave it in and replace it at your leisure or buy one and send mine back. Hopefully I'll never need it, kinda like insurance.
Bought it from Mid America.
I've already replaced 2 of mine. One on my 25 mile Pace Car
Aceco was nice enough to check my old ones but both needed an obsolete part.As for zeroing them out, mine were simply a matter of having the ignition switch 'on' and pulling the needle off and reinstalling at 'zero'.
Be carefull with the needle, they're fragile. Don't ask how I know
If you'd like to 'borrow' a new board to check things out, I got a spare one(always prepared!)
Try it, if it works either leave it in and replace it at your leisure or buy one and send mine back. Hopefully I'll never need it, kinda like insurance.
Bought it from Mid America.
Thread Starter
Le Mans Master
Joined: Oct 2005
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From: Glen Allen, VA
Ok, back on this one now. I have installed a new tach board, thanks to KapSA. I can't get the tach to zero. I have removed and reinstalled the needle to 0 with the signal wire disconnected per Wilcox's instructions. After doing that, when you turn the key on, the tach goes to about 3000. I'm wondering if I killed the inner workings of the tach, becuase in the boards instructions, it very specifically says not to swing the needle at all if you have to remove it to zero it. Well, that was all but impossible, so the needle did move. So, my question is what do I do now?
Safety Car
Joined: Jun 2004
Posts: 4,374
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From: Beecher Illinois
Basically, when you turn the key when starting the motor, the tach should read zero until the motor starts. When you stop the motor, the tach usually reads what it was idling at when shut off. Turn the key back to 'on' and it goes to zero again.
I know on the aftermarket boards I've replaced, there was a type of adjustment. But it was glued so as not to be user adjusted. Manufacturer apparently sets it up.
I did pull the needle on and off several times on one Vette to get it perfectly at zero(that's how I know they are fragile
)The other one I did didn't need to be reset, read correct right off.
Thread Starter
Le Mans Master
Joined: Oct 2005
Posts: 6,247
Likes: 471
From: Glen Allen, VA
Thread Starter
Le Mans Master
Joined: Oct 2005
Posts: 6,247
Likes: 471
From: Glen Allen, VA
ok, I'm out in the garage right now, and i've reset the needle to 0 about 10 times, and each time, after I reconnect the tach signal wire and turn the key on it goes straigt to about 3000. Both my old tach board and the one KapSA is letting me borrow are doing that. Anyone have any ideas? The old tach board didn't do that before I took it apart. Right now, I'd be happy just ot get it back like it was with my old tach board before I took anything apart.
Last edited by C3 4ME; Apr 6, 2010 at 06:04 PM.
Safety Car
Joined: Jun 2004
Posts: 4,374
Likes: 224
From: Beecher Illinois
ok, I'm out in the garage right now, and i've reset the needle to 0 about 10 times, and each time, after I reconnect the tach signal wire and turn the key on it goes straigt to about 3000. Both my old tach board and the one KapSA is letting me borrow are doing that. Anyone have any ideas? The old tach board didn't do that before I took it apart. Right now, I'd be happy just ot get it back like it was with my old tach board before I took anything apart.
Everything should be connected when you turn the key 'on' and pull the needle off.