Trouble shooting tach

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Well-known member
May 23, 2022
Reaction score
Ogden, UT
My Car
1971 Mach1 429SCJ Ram Air Drag Pak
Hi, is there a process to troubleshoot a non-working factory tach?
Not really. If you unplug the tach and use an ohm meter across the two leads you should get resistance. If no resistance the board is bad.
If you have resistance of 1 ohm and the car will start and run but the tach doesn't move, yup, you guessed it - the board is bad.
If the needle doesn't move freely (float) the movement is bad.
Fixed my tach issue. I am using a Pertronix 2 ignition and had the ignition module wired to the + side of the coil, along with the stock tach feed wire. I removed the P2 from the coil and wired the ignitor direct. Tach now works!