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What should tach read?
Thread Starter
Racer
Joined: Sep 2008
Posts: 353
Likes: 0
From: West Point MS
What should tach read?
I just put a new tach circuit board in my 75 this past weekend and zero'd it per the instructions that came with the circuit board. I put the dash back in and turned the key on and the tach needle was below 0. Is this OK or should I pull it back out and redo it?
Thread Starter
Racer
Joined: Sep 2008
Posts: 353
Likes: 0
From: West Point MS
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
The needle needs to be pulled off, power applied to the tach with no signal and then you need to re-install the needle on zero!
The tach zeroed out when you applied power but if it went below zero on the tach it will read wrong across the scale.
Willcox!
The tach zeroed out when you applied power but if it went below zero on the tach it will read wrong across the scale.
Willcox!
Le Mans Master
Joined: Sep 2002
Posts: 5,236
Likes: 898
From: Myrtle Beach SC
Tim...I'm curious. Had you buttoned the dash back or up or just enough to test the tach?
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Safety Car
Joined: May 2008
Posts: 3,753
Likes: 721
From: Lafayette Louisiana
76 tach replacement
I just did this on my 76 and it took a couple of episodes to get the tach pointer set right. I also checked the zero point and cross checked the reading at 1000 to 2000rpm with a separate meter. Mine from Mid America was off 100-200rpm on one side or the other, so I split the difference on the needle placement.
I suggest you might want to crank it and get the tach pointer like you want it with the instr panel not installed and resting on something to avoid multible instr panel installations. On the other hand after a lot of practice, I got to where I could install the instrument panel pretty quick!
Good luck!
I suggest you might want to crank it and get the tach pointer like you want it with the instr panel not installed and resting on something to avoid multible instr panel installations. On the other hand after a lot of practice, I got to where I could install the instrument panel pretty quick!
Good luck!
Last edited by 20mercury; Feb 13, 2009 at 09:44 AM.
Thread Starter
Racer
Joined: Sep 2008
Posts: 353
Likes: 0
From: West Point MS
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
20 Merc.
There is no need to split hairs here. On the board is a potentiometer (We calibrate ours before we send them out) that can be used to adjust the tach reading. You can dial this thing in to be dead on!
In the picture below it’s located in the left hand upper corner. You can adjust the calibration of each tach by turning this. It will damper or increase the signal to the tach board.
Tim:
If you zero the board out and install the needle, test it again to make sure. If the needle still fails to go to zero I’m afraid you may have a problem with the internal part of the tach. You should always power up the tach before installing it back in the dash to make sure it zeros out and just as a safety measure you might want to hard wire it before installing to test it.
If you don’t figure this out, drop me an email. Willcoxcustomerservice@Willcoxcorvette.c om
Willcox Inc.
There is no need to split hairs here. On the board is a potentiometer (We calibrate ours before we send them out) that can be used to adjust the tach reading. You can dial this thing in to be dead on!
In the picture below it’s located in the left hand upper corner. You can adjust the calibration of each tach by turning this. It will damper or increase the signal to the tach board.
Tim:
If you zero the board out and install the needle, test it again to make sure. If the needle still fails to go to zero I’m afraid you may have a problem with the internal part of the tach. You should always power up the tach before installing it back in the dash to make sure it zeros out and just as a safety measure you might want to hard wire it before installing to test it.
If you don’t figure this out, drop me an email. Willcoxcustomerservice@Willcoxcorvette.c om
Willcox Inc.
Last edited by Willcox Corvette; Apr 15, 2009 at 11:11 PM.
Safety Car
Joined: May 2008
Posts: 3,753
Likes: 721
From: Lafayette Louisiana
Thanks for the info.
Much thanks for the info, this is really good to know. 
20 Merc.
There is no need to split hairs here. On the board is a potentiometer (We calibrate ours before we send them out) that can be used to adjust the tach reading. You can dial this thing in to be dead on!
In the picture below it’s located in the left hand upper corner. You can adjust the calibration of each tach by turning this. It will damper or increase the signal to the tach board.
Tim:
If you zero the board out and install the needle, test it again to make sure. If the needle still fails to go to zero I’m afraid you may have a problem with the internal part of the tach. You should always power up the tach before installing it back in the dash to make sure it zeros out and just as a safety measure you might want to hard wire it before installing to test it.
If you don’t figure this out, drop me an email. Willcoxcustomerservice@Willcoxcorvette.c om
Willcox Inc.
There is no need to split hairs here. On the board is a potentiometer (We calibrate ours before we send them out) that can be used to adjust the tach reading. You can dial this thing in to be dead on!
In the picture below it’s located in the left hand upper corner. You can adjust the calibration of each tach by turning this. It will damper or increase the signal to the tach board.
Tim:
If you zero the board out and install the needle, test it again to make sure. If the needle still fails to go to zero I’m afraid you may have a problem with the internal part of the tach. You should always power up the tach before installing it back in the dash to make sure it zeros out and just as a safety measure you might want to hard wire it before installing to test it.
If you don’t figure this out, drop me an email. Willcoxcustomerservice@Willcoxcorvette.c om
Willcox Inc.
Thread Starter
Racer
Joined: Sep 2008
Posts: 353
Likes: 0
From: West Point MS
Thanks to all for the help. I pulled the tach back out and removed it from the dash panel, plugged it up to the tach wires and removed the needle. Cut the ignition on and put the needle back on at zero. I cut the ignition off and moved the needle by hand, cut the ignition back on and the needle went to zero.