Factory Tachometer is Overreading

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dboldt

dboldt

Douglas Boldt
Joined
Sep 9, 2009
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Erie, PA
Hello everybody! I just installed a factory tach into my 67 barracuda which has electronic 'orangebox' ignition. I found the tach on eBay. It works fine, but when I give it even a little gas, it jumps up to 4-5k RPM which is obviously wrong. I did some forum searching and found some threads talking about special sending units and calibration, and I'm looking for a little more information please.

Thank you in advance :)
 
Found the answer on Autometer's website with the help of Google.

If you have a Mopar Orange or Chrome Box ignition system on your vehicle, rather than connecting the Green signal wire of your tachometer to the negative side of your ignition coil, instead locate the Gray wire running between the Ignition Box and the Distributor. Connect your tach's Green signal wire to this Gray wire for a proper engine RPM signal.
Click to expand...
 
Yep, the old proverb strikes again.......
" If at 1st it doesn't work, use a bigger hammer..............
...................................... If all else fails, read the directions!"
 
Well, it's not an autometer tachometer, but I think the solution is correct.

Congrats on the 1k posts, btw :D
 
unfortunately, when I hook it up like autometer's site recommends, it does nothing. What a pain in the ***.
 
dboldt said:
Found the answer on Autometer's website with the help of Google.
Click to expand...

Can't imagine why that would work. You will get the same plus rate at the grey wire as you would at the neg of the coil and will likely not get enough voltage on the grey wire to trigger the tach. I have never had an issue with tachs working properly on the neg of the coil regardless of the mopar box.

That being said I played with a factory tach on my 68 Barracuda and gave up because the movement was so slow it couldn't keep up. I purchased a reproduction tach with a modern movement to go in the hole in the dash.

If you want to try and get the factory tach working these guys have a replacement circuit board that has two pots that you adjust to calibrate it.

http://www.realtimeengineering.com/mopar/tachboard/tachboard.htm
 
I have one of RTE's reproduction tachs and the Orange box and the tach appears to work just fine.
 
I have placed an order from Greg for the RTE board, and will swap it out!

Thank you all for your help! I totally appreciate it!
 
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