620 tach testing

[laniadude]

I have a 74 620 and i recently got a stock tach to put in. I wired it up like how the other topics in this forum showed ( power, ground, and - side of coil). I got the lights to come on but no movement on the needle. I have also heard that you can hook it up to the positive side of the coil instead of the negative, but I didn't want to try it in case it burns up the tach. How do I test the tach? If there is a way..

 

Thanks

[jefe de jefes]

Sounds right. Did you connect direct to the battery or through your wiring harness?

[laniadude]

i connected straight to the battery. Would it be a bad thing to hook up to the + side coil?

[jefe de jefes]

Idk

 

I always connect straight to bat + and - then - side of coil.

Try without the lighting(bulbs).

[banzai510(hainz)]

If you hooked it up to +side battery the Tach would be ON all the time(you cant tell but it would be powered up just no trigger input) and if the rotor on the dizzy is lined up right would drain the battery I would think.

Am I wrong here?Datzenmike?datsunaholic?

 

I would think you want +side of the coil or the +side of the Ballast resisitor(if running points or a pertronix) if anything or from a switchable 12volt when Key is in ON position. then when key OFF there no power routed to it.

[datsunaholic]

"Stock Tach"

 

Which version? The 620 "Stock tach" had both an inductive type (through '75) and a pulse type (76+). They are wired very differently.

[laniadude]

I'm not exactly sure...how do I tell?

[laniadude]

I. have a points distributor by the way. And there is no hook ups on my harness to just plug the tach in.. I had to splice into other wires in the dash...

[datzenmike]

Inductive type (I think) has to be wired between the - coil terminal and the points... Doug?

 

 

 

 

 

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