[John O]

I installed a new dash in my sons 66 C10 everything works great except I can not get the new Autometer tachometer to operate correctly.
I have a 454 Big block with a HEI distributor.
the crazy thing is we had an old tach mounted to the column that worked fine??
I even ran a new separate wire from the sending terminal and it still bounces goes high, low nothing consistent.
Anybody have any suggestions

thank you
John

 

[Dave S]

Should have a tach connection on the HEI? Are you running a box or not? Did you install the tach in your new dash? Maybe you lost a wire? And check for good ground.

How to Install a Tachometer

With some exceptions, namely older diesels and Corvettes, most tachometers use electrical pulses from the ignition system to indicate an engine’s rpm. Though this method delivers an accurate reading, installing …

www.onallcylinders.com

 

[John O]

No box, I have the wire right to the terminal on the cap. I ordered an online filter to see if it will help. Can the cap, coil itself be sending a bad signal? The old tach I took out worked.
Thank you

 

[Dave S]

Did you see the link I added? I may have been editing while you were replying? Check the wiring in the link. And make sure you have correct tach for 8cyl.

 

[John O]

I will go through it when I get home, the tach is set for 8cyl
I ran a separate wire from the cap to rule out a wire issue, the only thing I have not done is run a dedicated ground. I will give that a shot and report back.

thank you for the help

 

[Dave S]

You could also temp hook up the old tach to make sure signal from hei is good.