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Which Tach terminal is Battery Positive

LowBikeMike

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1969 Road Runner, non rallye dash, factory tach. Can someone look under their dash and tell me which terminal is connected to the fuse box. A lot of threads mention long stud is positive, both of mine are same length. Others mention spade terminal goes to coil, as pictured no spade terminal. If no pics, anyone know how I can determine which stud goes to battery power?

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Here is a picture showing which one is the spade terminal. I can’t help you any further, the tach and I are in Michigan and the car is in Kentucky
 
I would think if you took a volt meter to one of the studs + to the - side of the battery it should move the needle and ultimately tell you which stud is positive.
 
Thanks for the photo, it matches a similiar photo I found online with the plastic cover but no spade terminal, guess it was broke off.

With tach in hand, voltmeter positive to either stud with voltmeter negative to battery ground results in no tach pointer movement or reading on voltmeter. I know the tach works because it was installed prior, just forgot which terminal was which.

Still would appreciate it someone peeked under their dash and took a look at their working setup.
 
View attachment 1160365 Here is a picture showing which one is the spade terminal. I can’t help you any further, the tach and I are in Michigan and the car is in Kentucky
The spade terminal should be the coil negative wire - and the plain stud is 12 Volts positive.

Happy to be corrected. :thumbsup:
 
I understand the spade terminal goes to the coil, are you saying the photo posted shows the spade on the correct terminal?
 
As a follow up, I found pictures of this style tach with the spade on either terminal, so not being conclusive I did a bit more research, including taking mine apart. I found the signal terminal (attached to ignition coil) is brass in color while the positive terminal is steel colored. Age makes the terminal look the same, but if you remove the nuts you can see one is actually brass colored. Thanks for all that helped on this topic.
 
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