tach install, i know its been covered, but I can't find my answer

[jwerty1]

74 620, trying to rehook up my tach.  It was installed by the previous owner and I disconnected it when I pulled my engine the other year and haven't gotten it hooked back up yet.  I did some reading, however for whatever reason I'm not grasping the concept.  It's a loop wire Datsun tach.  I have my factory points distributor, however I have the pertronix kit installed and also the pertronix coil.  The ballast resistor was taken out.  Where, exactly, do I wire the two wires coming off the tach?   A specific diagram would be wonderful.  Yes I have searched and looked at several different write ups, yes I have tried a handful of things, I'm just not sure exactly what to do.  I know they are supposed to be hooked in series, but for whatever reason I'm not fully grasping that.  Thank you.

[LenRobertson]

I had this thread Bookmarked: http://community.ratsun.net/topic/16328-how-to-wire-factory-tach-with-matchbox-distributor/

mklotz70 in post #10 seems to give a clear explanation. It sounds like just take the neg wire off the coil and hook to one tach white wire, then hook the other tach white wire back to the coil. Reverse the white wires if it doesn't work. But I haven't hooked up mine yet, so maybe it isn't so simple. I just looked at it and there aren't any white wires, but two black and white wires I'm pretty sure do the same thing. I can see they loop through a little thingy on the back of the tach.

 

There are wiring diagrams here: http://www.davidcmurphy.com/olddat/620tech.htm

but I don't know if any show the wiring for the tach.

 

If you figure out your hookup, please post what worked for you.

 

Len

[ggzilla]

It's a loop wire Datsun tach

Those are wired differently than most tachs. Wire it inline with the IGN feed wire. It's probably a Datsun 1200 tachometer, which looks much like a 620, but wired differently.

 

 

See http://datsun1200.com/modules/mediawiki/index.php?title=Tachometer_Wiring

[datzenmike]

Welcome back.

[jwerty1]

thank you thank you.  I don't know why I wasn't getting that from what I've read.  However, hooked it up and it didn't work, so I changed polarity and it worked fine.  Turns out my idle was set just about right by ear :thumbup: .  However, I wish I had a slightly smaller turbo as it doesn't boost much until after 4k.  O well, just getting the bugs worked out anyhow.  Thank you!