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Discussion Starter #1
I have a 1970 Chevelle SS 396 with factory gauges. This past winter I removed the cluster to convert the clock to quartz and calibrate the gauges. Everything, with the exception of the clock worked when I removed them. Upon reinstalling the cluster everything works fine with the exception of the tach. I had the "Tachman" in Georgia do the work and he suggested that I check the (3) grounds coming off the cluster. As near as I can tell I have (2) grounds, the main plug attached to the cluster, and the power connection for the clock. Where should the (3) grounds come off the cluster? The tach does light up when the headlights are turned on. Could anyone tell me what might be wrong? Any Ideas would be greatly appreciated!
 

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If the other gauges are working you have power and ground to the cluster. Ground for the cluster is provided by the ground strap that is attached to the headlight switch, wiper switch then the actual ground at the metal dash frame. You might try taking a wire and touching one end the back of the tach housing and the other end to a good chassis ground. Make sure something didn't happen to the tach wire that comes out of the dash harness and passes through the firewall to the negative coil terminal. The dash lights are a separate circuit and wouln't have anything to do with the tach working.
 

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Discussion Starter #3
Thank You! I'll try grounding a wire to the back of the tach and I'll also trace the wire going to the negative side of the coil. I did drop the dash so it's possible that it may have gotten pinched.
 

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Dropped the dash and traced the wires, everything checks out. The brown wire going from the wiring harness to the negative side of the coil looks fine. I also removed the connections and applied di-electric grease to them. Is there any way to check the wire? Also, would it be possible that the coil isn't sending a signal to the tach? Could the coil be at fault? I'm stumped! The unit worked fine when it was bench tested prior to "The Tachman" shipping it back to me. I'm up for any ideas you guys might have as I don't claim to be an electrician.

Thanks,
Todd
 

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Discussion Starter #5
Dropped the dash and traced the wires, everything checks out. The brown wire going from the wiring harness to the negative side of the coil looks fine. I also removed the connections and applied di-electric grease to them. Is there any way to check the wire? Also, would it be possible that the coil isn't sending a signal to the tach? Could the coil be at fault? I'm stumped! The unit worked fine when it was bench tested prior to "The Tachman" shipping it back to me. I'm up for any ideas you guys might have as I don't claim to be an electrician.

Thanks,
Todd
 

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Discussion Starter #6
I found my problem! I removed my tach from the cluster and one the nut securing the 12V stud on the back of the tach was a little loose (the stud goes through the printed circuit and is secured with another nut). I tightened it up and my grief was over!

Thanks for Helping,
Todd
 
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