Electric Tach Calibration/Error
Thread Starter
Drifting
Joined: Dec 2004
Posts: 1,714
Likes: 42
From: Austin Texas
Electric Tach Calibration/Error
I had my mechanical tach professionally converted to electric. It has worked well for the last 500 miles since I installed it until today.
My dad and I went out for a drive and I was going about 60-65 mph and I saw the tach was at about 5K. The motor was not going that fast. Here is what I can tell
Before, tach read about 600 at idle. now reads 8-900 at idle.
now, seems to behave normal until I reach 2500 rpm, then over that it will spin from 2500-5000 just between 60 and 70 mph.
I checked the connection at the distributor but really dont know what else to suspect.
The work is under warranty but as you know its not an easy part to remove if I can avoid it.
thanks!
john
My dad and I went out for a drive and I was going about 60-65 mph and I saw the tach was at about 5K. The motor was not going that fast. Here is what I can tell
Before, tach read about 600 at idle. now reads 8-900 at idle.
now, seems to behave normal until I reach 2500 rpm, then over that it will spin from 2500-5000 just between 60 and 70 mph.
I checked the connection at the distributor but really dont know what else to suspect.
The work is under warranty but as you know its not an easy part to remove if I can avoid it.
thanks!
john
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
John,
I most cases this is a sign of a board failure. Either in the chip or the pot that controls the adjustment! If the tach is working at all it is getting power, ground and signal. The issue on the board is how the input signal is being converted.
It is possible for the potentiometer to have moved and this is one of the main reasons we use a 15 turn pot on our boards! Other boards use a 1 turn potentiometer and it is possible for you to flick the pot with your finger and make the calibration change.
If you want to send this in to me I can put it on the tester here and tell you what is wrong with it! There is no charge for this. Problem is it's a 1975-1976 board and boy.. they are a pain to get out.
Willcox
I most cases this is a sign of a board failure. Either in the chip or the pot that controls the adjustment! If the tach is working at all it is getting power, ground and signal. The issue on the board is how the input signal is being converted.
It is possible for the potentiometer to have moved and this is one of the main reasons we use a 15 turn pot on our boards! Other boards use a 1 turn potentiometer and it is possible for you to flick the pot with your finger and make the calibration change.
If you want to send this in to me I can put it on the tester here and tell you what is wrong with it! There is no charge for this. Problem is it's a 1975-1976 board and boy.. they are a pain to get out.
Willcox
