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Discussion Starter #1
I hooked up a brand new AtorMeter tach the other day. When the ignition is turned on the needle jumps to zero like it should. But when the engine is started it stays on zero.

Anyone know of a way to check the MSD box (6A), or the tach for proper operation while it's installed in my truck ? I took my time installing the tach, hiding all wires, and hooking the tach light to my dash lights so it dims and comes on and off with them. I really don't want to rip it out only to find my box is bad. I'm hoping someone here knows a way to check one or the other for proper operation. Thanks.
 

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The tach output on the end of my box goes right to the tach,not the coil. I had a similar deal that turned out to be a bad ground. make sure the tach has it's own ground ,ran mine to the batt - & works perfect . when I shut off my engine the needle stays where my idle speed is, about 1100 rpm, when I turn the keyswitch to on it goes back to O
 

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Sounds like you have the tach signal wire connected to the coil. If so plug it into the side of the MSD box "Tach output". The Msd box fires multiple sparks and the tach doesn't know what to do so it does nothing!

Or a loose ground, and it's tring to ground through the light.

If it is a bad ground it will act up when you mess with the light dimmer switch. If it is a bad signal it will only do as you say.
 

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Discussion Starter #6
Thanks for the help guys. I did in fact hook up the tach to the tach output of the MSD box. The tach is the smaller 3 3/4" type, mounted to my steering column. I will check the ground again, but I'm 99.999999% sure it's good. I had to extend the wire to the box, and verified continuity from the splice to the box.
 

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Might want to call Autometer and ask what other test you might be able to do to see it it is your MSD or tach.

The only other thing I can think of is to check and make sure the tach is switched for V8.
 

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i have seen where the autometer-autogauge models have a filter or adapter they sell if this problem happens you need to check the instruction that came with tach its usually on the capatability page.
 
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