73 challenger with Rally dash, tack wiring question.

[Copilot]

Which wire connects to the post on the back of the tac, is it the negative from the coil? I want to test it on my charger and don't want to damage anything.
Thanks in advance.

 

[Ricks72Chlgr440]

Which wire connects to the post on the back of the tac, is it the negative from the coil? I want to test it on my charger and don't want to damage anything.
Thanks in advance.

Coil negative is what you want

 

[Copilot]

Coil negative is what you want

Hi, yes I know coil neg. but which connection on the back of the tac is for coil negative, is it the spade connector or is it the post.
Thanks

 

[Challenger RTA]

Wire

 

[Katfish]

Fig 8 isn't helpful, they have DBL going to both terminals.
To be sure I'd take an ohm meter and see which 1 has continuity to 12V connection.

 

[Challenger RTA]

72-74 cluster

 

[Vaanth]

Which wire connects to the post on the back of the tac, is it the negative from the coil? I want to test it on my charger and don't want to damage anything.
Thanks in advance.

It sounds like you want to "bench test" your E-body tachometer using the running engine under hood in your Charger. In this case, connect as follows and referring to the adjusted borrowed image (from post #6):

• Connect +12 volts from the Charger to the post, circled in red in the image.
• Connect the negative (-) terminal of the Charger's coil to the spade terminal, circled in green in the image.
• Connect ground from the Charger to the tachometer metal housing or mounting nuts, or any spot of the metal housing of the instrument cluster if still mounted in it.

 

[Copilot]

It sounds like you want to "bench test" your E-body tachometer using the running engine under hood in your Charger. In this case, connect as follows and referring to the adjusted borrowed image (from post #6):

• Connect +12 volts from the Charger to the post, circled in red in the image.
• Connect the negative (-) terminal of the Charger's coil to the spade terminal, circled in green in the image.
• Connect ground from the Charger to the tachometer metal housing or mounting nuts, or any spot of the metal housing of the instrument cluster if still mounted in it.

View attachment 142586

Thank you, that is what I was looking for.