tach install trouble

[Ironangel]

Originally Posted by toolboxchev

Get rid of that Chinese junk and buy a Sun Rach

Maybe you should take some spelling lessons? ...Which of the three tach signal hook up options are you using? Preferably #1, green wire to the (-) negative terminal of the coil. Make sure the tach is grounded to the firewall. Also make sure your battery is grounded to the motor, and the motor to the cab, and cab to frame! Follow the instructions for the red to switched power, and the white to the cluster terminal. Both are available on the fuse box...What distributor do you have? Is it an HEI with the coil built in? One last thing, most tachs have a switch for 4, 6, or 8 cylinder somewhere on the back, does yours? If none of the above works, you may be committed to using one of the inductive pick up options rather than the green wire to negative terminal on the coil...In other words, that tach may be a 6 cylinder tach...And rather than fuss with trying to mount it behind the cluster panel, just mount it to the column in front of the cluster...?

[SC1969c10]

It does have the adjustable cylinder option. Messed with that on the first one only to find out from the help line that they come out of the box ready for a v8. I went green wire direct to the distributor. Also tried the inductive to see if I was missing something, but that registered no RPMs. I will run through all the grounds, i know the only one im questioning is the tach is grounded to the metal gauge cluster.

The previous owner cut out a hole and mounted the tach in the center, otherwise I wouldnt have a problem mounting it else where.

And i had to laugh as I knew someone would say something like that
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[DeBattista]

I would recommend hooking the green wire to the negative of the coil instead of the distributor itself, like you're thinking there maybe something odd going on with the dizzy and that's freaking out the tach. It should be a quick and easy transfer just to try it out and see if it works.

[kwmech]

Appears to be an HEI dizzy, only one place to hook it up

[DeBattista]

Originally Posted by kwmech

Appears to be an HEI dizzy, only one place to hook it up

Ah didn't see that part.

[dagnabbitt]

Originally Posted by Ironangel

Also make sure your battery is grounded to the motor, and the motor to the cab, and cab to frame!

I second that. If it already looks like you have the grounds there, check them for corrosion and replace them. I would also ground the motor to the frame with a hefty strap for good measure. I did it when I put my NVU gauges in and experienced the problem you are having: and it straightened right out. And anyway, adding and checking grounds is never a waste of time or money.

[SC1969c10]

Well i checked all grounds, everything was grounded by previous owner, so good on him. I even went and ran new grommets to make sure lines were secure. Checked tach, same deal. So i took the dash back out and grounded tach to the cab, still reading the same. So ran a wire from tach to battery ground and it jumped down 500 rpm idling at 35-4500. So for sake of experiment i took the ground of and the needle holds at 4000 then moves and stays still on 5, and then back to still on 4.

HEI distributor with a “idiot proof” spot for the tach’s green wire.
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