Tach or Tach board?
Thread Starter
6th Gear
Joined: Jun 2019
Posts: 6
Likes: 0
From: Central Jersey
Tach or Tach board?
Hi everyone,
I’m trying to determine if my tachometer or my tach board is bad. I’m working on my 81 with an aftermarket distributor and no filter. Originally the problem was that the tach stayed at around 6300 rpm’s at all time, whether the car was running or off. I pulled the tach from the dash and if I manually move the needle it would stay wherever I left it until I Added power, Then it would jump back to 6300. If I move the hand below 6300 it would go up, if I moved the hand above it would move down. I pulled the needle off and zeroed it so now it always goes to zero when powered up. I checked my signal wire for continuity and it checks good. Then I checked my signal with a multi meter set to AC volts and with the engine idle I got approximately 8 Volts. As I increased the engine speed the voltage also increased so I’m assuming my signal Is good. I may be wrong here, but I thought when the power is turn off the tachometer should read around 700 and then go to zero when powered up. Mine never moves. I Tested all the traces on the printed circuit board and they checked out fine.
Any advice on these symptoms which I should start with?
I’m trying to determine if my tachometer or my tach board is bad. I’m working on my 81 with an aftermarket distributor and no filter. Originally the problem was that the tach stayed at around 6300 rpm’s at all time, whether the car was running or off. I pulled the tach from the dash and if I manually move the needle it would stay wherever I left it until I Added power, Then it would jump back to 6300. If I move the hand below 6300 it would go up, if I moved the hand above it would move down. I pulled the needle off and zeroed it so now it always goes to zero when powered up. I checked my signal wire for continuity and it checks good. Then I checked my signal with a multi meter set to AC volts and with the engine idle I got approximately 8 Volts. As I increased the engine speed the voltage also increased so I’m assuming my signal Is good. I may be wrong here, but I thought when the power is turn off the tachometer should read around 700 and then go to zero when powered up. Mine never moves. I Tested all the traces on the printed circuit board and they checked out fine.
Any advice on these symptoms which I should start with?
Le Mans Master
Joined: Sep 2002
Posts: 5,236
Likes: 898
From: Myrtle Beach SC
Well, you've conducted quite a bit of troubleshooting. It's estimated that 90 percent of the time...it's the tach board. Get a tach board from Wilcox for $54.00 and replace it. See if that corrects your issues. 
