1976 Tach ICB Replacement
Thread Starter
Heel & Toe
Joined: Aug 2004
Posts: 21
Likes: 0
1976 Tach ICB Replacement
Just replaced my tach ICB with a Nordskog one sold by Eckler's. With the original ICB, the needle was always stuck at 5. Now, with car turned off, the needle is at 26. With car running, needle is almost at 30 regardless of engine speed. What else might be wrong?
Le Mans Master
Joined: Jun 2002
Posts: 8,339
Likes: 24
From: I can walk to MA
I vaguely recall a good post on the tach circuit boards.
It discussed the different brands and an adjustment feature
that was deemed useless for "zeroing".
Try reading this ... talks about powerign up the tach and re-zeroing by removing/installing the needle:
http://www.corvettefaq.com/c3/RebuildSpeedo.htm
It discussed the different brands and an adjustment feature
that was deemed useless for "zeroing".
Try reading this ... talks about powerign up the tach and re-zeroing by removing/installing the needle:
http://www.corvettefaq.com/c3/RebuildSpeedo.htm
Melting Slicks
Joined: Apr 1999
Posts: 2,010
Likes: 3
From: Moon Twp. PA USA
Replaced the tach board in my '76 and had to rezero the tach. Got the board from the good doctor (Docrebuild) and it included a note saying that the board rebuilder would guarantee a working tach if you sent him the board and your tach and some money. I did not have to do that as everything worked out of box.
Team Owner
Joined: Apr 2001
Posts: 54,204
Likes: 180
From: S.W. Ohio. . . . . . NRA Life Member
Most original C3 tach boards had 2 and sometimes 3 "scratch" carbon calibrators. One for zero, one for 3000rpm, and one for redline rpm.
The new circuit boards only have one calibration control - and that's for redline RPM calibration. The only way to calibrate "zero" with the new board is to power up the tach - without any engine pulses present - remove the needle, and put it back on with it pointing to zero.
I just repaired a 1975 tach that already had the board replaced but it wasn't zero'd properly - obviously giving false readings with the engine running.
The replacement circuit boards mfgr'd by Wilcox IMO are not engineered very well (and I won't use this particular mfgr at all in any repairs or conversions). The redline calibration control has WAY TOO MUCH control. One slight bump and the calibration can jump 400 or more RPM. I take some of the sensitivity out of the control and it calibrates rather nicely, and seems to hold calibration a lot better.
I will test and calibrate your 1975-1977 tach with your new circuit board for $45 including return shipping.
email me if interested: tim-yvonne@juno.com
The new circuit boards only have one calibration control - and that's for redline RPM calibration. The only way to calibrate "zero" with the new board is to power up the tach - without any engine pulses present - remove the needle, and put it back on with it pointing to zero.
I just repaired a 1975 tach that already had the board replaced but it wasn't zero'd properly - obviously giving false readings with the engine running.
The replacement circuit boards mfgr'd by Wilcox IMO are not engineered very well (and I won't use this particular mfgr at all in any repairs or conversions). The redline calibration control has WAY TOO MUCH control. One slight bump and the calibration can jump 400 or more RPM. I take some of the sensitivity out of the control and it calibrates rather nicely, and seems to hold calibration a lot better.
I will test and calibrate your 1975-1977 tach with your new circuit board for $45 including return shipping.
email me if interested: tim-yvonne@juno.com
