79 L48 Tach
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
I don't know that I would call that a working tach.
First, disconnect the battery, and turn the key through IGN and hold it in start for 30 seconds. This will ensure that the tach has absolutely NO power. Then, reconnect the battery and start the engine.
if it still does the same thing your tach circuit board might be kaput. There are reproductions available but I have heard of lots of problems getting them calibrated properly. I think you should try to find a used original one.
Drifting
Joined: Nov 2003
Posts: 1,634
Likes: 4
From: Northern NJ
St. Jude Donor '04 & '05
It is not unusual for the factory tach boards to go bad. There are a couple components that commonly go bad. However sometimes the chip on the board goes bad too, and that chip is now an obsolete part and no longer available. Replacement boards sometimes work, but often don't read correctly.
Are there any darkened/burnt spots on the printed circuit board itself? If so the board is probably repairable. The pic below shows a fellow forum members tach board before it was repaired.
It looks like a goner but ones that look like this are typically the ones that can be repaired.
If you want more info on possibly repairing it, please feel free to PM me.
Good Luck!
Are there any darkened/burnt spots on the printed circuit board itself? If so the board is probably repairable. The pic below shows a fellow forum members tach board before it was repaired.
It looks like a goner but ones that look like this are typically the ones that can be repaired.
If you want more info on possibly repairing it, please feel free to PM me.
Good Luck!
Listen to this guy...he knows his stuff. 
