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Discussion Starter #1
Hi I am restoring my 65 Chevelle and reinstalling the SW tach I bought back in the 60's but I cannot remember for sure how to wire it. It is installed in the centre of my gauge cluster, grounded to the cluster which is grounded to the firewall. The tach has 3 wires (which I have changed and colours don't necessarily match correctly; however, one is green which I believe is power connected to the ignition on. The other two are red and white connected to the positive and negative sides of the sending unit inside the tach cover. I believe that the red should go to the positive side of the coil and the white to the negative side of the coil. Would someone please verify this for me or correct me where I went wrong. Thanks Tim
 

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Bill
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Not sure about your tach but everyone that I have seen used red for positive, black for negative, white for panel light, and green for negative side of the coil.
 

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Are you sure your tach is not one that needs a sending unit mounted under the hood? It looks like an early model voltage regulator. Just asking.
 

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Discussion Starter #4
I know that's why I'm having a problem. Someone, likely me, changed the wires at some point. The tach now has only 3 wires - the green which I think is the power/hot/ battery positive wire which should be connected to the on position of the ignition switch, a red wire which is connected to the + side of the sending unit and a white wire which is connected to the - negative side of the sending unit. (I think that the sending unit the small block about 1" x 1.5" inside the back case of the tach) there is no other sending unit which was mounted on the firewall or inner fender.)
 

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My mid-sixties SW tach has a + and - terminals on the back. They go to a red sending unit which also has + and - terminals plus a third terminal which goes to the coil.
A third wire from the tach is for lighting.

Have you tried googling the model number of your tach? You may be surprised to find wiring diagrams out there.
 

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Discussion Starter #6
Yes I tried googling and just got Ebay, but I did finally figure out the wiring - just took off the cover and there and behold were the instructions right on the sending unit - negative (white) to ground, + (red) to primary side of coil and other (black not green) was connected to the light. It pays to pay attention to before reassembling old parts - I have learned my lesson. Thanks everyone for your help. Tim
 
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