What makes a tach turn "backwards"?!
Thread Starter
Melting Slicks
Joined: Jan 2003
Posts: 2,877
Likes: 13
From: Doha
St. Jude Donor '08
What makes a tach turn "backwards"?!
A friend of mine is restoring a '76, he just installed the dash components and yesterday he started the engine for the 1st time, we were surprised to see the tach is moving backwards! .. at idle it stays at 700 RPM but when we rev the engine it turns the other way towards zero, he put a new board there (from Willcox) and zeroed the tach exactly as recommended, is there a polarity that have to be swapped somewhere???
Team Owner
Joined: Jun 2000
Posts: 38,923
Likes: 1,482
From: Southbound
Cruise-In II Veteran
Electromagnetic discharge from a nuclear explosion...or a failing tach board. Contact Willcox. They had a problem with some of their boards and they'll set things right with you if it's the board.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
A friend of mine is restoring a '76, he just installed the dash components and yesterday he started the engine for the 1st time, we were surprised to see the tach is moving backwards! .. at idle it stays at 700 RPM but when we rev the engine it turns the other way towards zero, he put a new board there (from Willcox) and zeroed the tach exactly as recommended, is there a polarity that have to be swapped somewhere???
Who is the customer and when did he buy the board.
There was a small sample of boards that had a bad capacitor on them but they would die out at around 2000 and start drifting back to zero. The issue was the supplier of one of the capacitors, and it was not bleeding off signal which in turn confused the chip. (best way I know to describe it),
If your friend wants to send the entire tach in to us, I'd be happy to put it on the machine and actually attach it to a running car for testing... If the board is a problem you know I'll take care of this n/c plus this allows me to calibrate match the board to the actual tach vs. using the industry standard.
Also.. this is the thread on the defective boards.. Hate to say it but it did happen on a small scale but on any scale it was a nightmare... I have to call it for what it is and it was a mess.....
So.. go take a look at this thread...... This deals with boards purchased before May 01, 2010.
http://forums.corvetteforum.com/c3-g...-question.html
Willcox
Last edited by Willcox Corvette; Nov 6, 2019 at 02:03 PM.
Thread Starter
Melting Slicks
Joined: Jan 2003
Posts: 2,877
Likes: 13
From: Doha
St. Jude Donor '08
Hamad-
Who is the customer and when did he buy the board.
The running backwards is actually impossible...
There was a small sample of boards that had a bad capacitor on them but they would die out at around 2000 and start drifting back to zero. The issue was the supplier of one of the capacitors, and it was not bleeding off signal which in turn confused the chip. (best way I know to describe it),
If your friend wants to send the entire tach in to us, I'd be happy to put it on the machine and actually attach it to a running car for testing... If the board is a problem you know I'll take care of this n/c plus this allows me to calibrate match the board to the actual tach vs. using the industry standard.
Also.. this is the thread on the defective boards.. Hate to say it but it did happen on a small scale but on any scale it was a nightmare... I have to call it for what it is and it was a mess.....
So.. go take a look at this thread...... This deals with boards purchased before May 01, 2010.
http://forums.corvetteforum.com/c3-g...-question.html
Willcox
Who is the customer and when did he buy the board.
The running backwards is actually impossible...
There was a small sample of boards that had a bad capacitor on them but they would die out at around 2000 and start drifting back to zero. The issue was the supplier of one of the capacitors, and it was not bleeding off signal which in turn confused the chip. (best way I know to describe it),
If your friend wants to send the entire tach in to us, I'd be happy to put it on the machine and actually attach it to a running car for testing... If the board is a problem you know I'll take care of this n/c plus this allows me to calibrate match the board to the actual tach vs. using the industry standard.
Also.. this is the thread on the defective boards.. Hate to say it but it did happen on a small scale but on any scale it was a nightmare... I have to call it for what it is and it was a mess.....
So.. go take a look at this thread...... This deals with boards purchased before May 01, 2010.
http://forums.corvetteforum.com/c3-g...-question.html
Willcox
If you are sure that its the board, then I would just buy another one, because shipping it back would cost me around 40 to 50 bux. One more option is to fix the board locally by replacing the faulty capacitor.
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Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Hamad-
Place the order in so that it will process tomorrow! I'll go in the order later today or early tomorrow and delete the cost of the board and all shipping....
I'm not going to have you repair our mistake and I'm not going to allow you to purchase another board...
It's on me... I'll make sure it ships no charge to you.
Willcox
Place the order in so that it will process tomorrow! I'll go in the order later today or early tomorrow and delete the cost of the board and all shipping....
I'm not going to have you repair our mistake and I'm not going to allow you to purchase another board...
It's on me... I'll make sure it ships no charge to you.
Willcox
Le Mans Master
Joined: Apr 2005
Posts: 6,359
Likes: 428
From: Seattle Area WA
That same thing happened to me with a new board. One of the pins that are riveted to the board was not making contact with the solder trace, I had to add solder to that area to make it work.
2nd Gear
Joined: May 2017
Posts: 2
Likes: 0
My tach is running backwards! It was trying to work when I first got it running, but shortly after it went to about 5 grand and just hovered around there. The car sat since 2005 so I figure a new board might be in order. I took it apart and cleaned all the connections and tried to zero it but now it sits on zero and goes negative when I rev it up.
