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Discussion Starter · #1 ·
I put in rebuilt gauges and the tach is not working. Question: what color wire connects to the coil for the tach? Also so I can test the instrument harness plug what color wire feeds the tach from the plug i would assume it would be the same that can from the coil? Right now the coil has a ground running to the fire wall and an orange wire running to a plug that attaches to the distributor. A red wire is connected to the + side running to the plug as well as an other red insulated wire that runs to the ignition. I unplug this and connected to the - but car would not start.

Any thought?
 

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The factory tach wire is brown, from the gauge connector then goes through the firewall to the - side of the coil. What distributor do you have? Points or HEI?
 

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Discussion Starter · #3 ·
HEI- I see a tan (could be brown) wire that has a female end with a round boot on the end running from a relay that is attached to the fire wall near the distributor. Running through the fire wall are a red and brown (tan) wire that attach to this relay. THe relay has two plugs. One the red and brown (tan) wire and the other the wire with the rubber boot on the end. The only connection to the - side of the coil is an orange wire that attaches to the distributor and a ground that attached to the fire wall.
Any thoughts.
 

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I'm assuming it's not a GM HEI distributor.

"The only connection to the - side of the coil is an orange wire that attaches to the distributor and a ground that attached to the fire wall."

There shouldn't be a ground wire attached to the -terminal of the coil.

Are you sure it's black and that it is attached to the firewall? The tach lead is dark brown and passes through the firewall in close proximity to the coil. It, the tach lead, will have a rubber grommet where it passes through the firewall.

Do you have any way to post a picture of the wiring? Maybe e-mail it? If you do e-mail be sure to include Chevelle in the subject line.
 

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Sounds like someone is using a relay to supply power to the hei and using the resistor wire to energize the relay. So you have an HEI with external coil? It will not start with the ground wire on the - coil, remove that. I would remove all the relay wiring and run a new wire from the ign terminal on the fuse block to the +12v terminal on the HEI.
 

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Discussion Starter · #6 ·
I have found the brown wire that passes through the fire wall and runs to the gauge and have connected to the - terminal of the distributor. I have power at the plug. When running and I test the plug the car shuts off. So I have power juice but no tach. The distributor is MSD not HEI like I stated earlier.
 

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Factory tach may not work with MSD. You might have to buy a tach filter. Also I think with msd there should be a tach terminal on the msd box.
 

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Discussion Starter · #8 ·
I don't have an MSD box just a distributor. I called MSD and they are going to send me something to fix the problem. You might be right that some type of filter is needed.
 
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