Odd Autometer Rev counter issue

[Lewis]

This one's got me!

Basically I set about installing and fitting my Autometer rev counter.

As per the majority of them, for 4 cylinder applications, you clip the brown and yellow (iirc) wire on the back to enable it to read right.

All the wiring is correct and the rev counter feed comes off the back of the Smiths tacho (which reads correctly) - and is the same feed off the -ve terminal off the coil.

However, the Autometer reads precisely TWICE that of actual engine RPMs.

Has anyone stumbled across this before?

I pulled the Autometer apart and found a few adjustment pots but I'm wary to start fiddling, especially when I've conformed to the instructions.

I will clip up the brown and yellow wires again tomorrow and connect them one at a time to see if I get any useful results but can't see that happening.

Very frustrating! Autometer's website and guides are of no help, it has more than 12v as required, a good ground, everything on it works spot on, it just reads twice as high! I did find reference to single and twin-pulse ignition readings but this doesn't appear to be the model that accounts for that and simply has a 4, 6 and 8 cylinder setting but seems to be reading like a two at the moment!

The car in question is a a Dolomite Sprint, fitted with the standard single coil and Luminition Magtronic ignition.

Apologies for it not being an 8 pot related inquiry

[katanaman]

has your car been rewired? Most of the old smiths rev counters worked with reading the amps taken from feeding the coil and not the actual pulses from the - of the coil. Yours of course could be different but it might be worth connecting your new rev counter to the - of the coil direct and see what you get.

[Lewis]

This is interesting - I did try and follow the wiring and it seems the Smiths takes it's feed direct from the -ve of the terminal, but following the wiring on a BL car and assuming it doesn't change at some point is like flipping a coin

Thanks for the heads up though - it was next on my list, so I'll give that a try now I've made up terminals for easy connection and disconnection

Cheers,
Lewis

[Lewis]

Fixed it! Disregarded the Autometer instructions and reconnected the brown wire (after trying various combinations).

Works fine, go figure!

Did a direct feed to the coil to check too but same result initially

[katanaman]

Glad you got it fixed.