Tach problem

[EZMachN]

I installed my Auto Gauge tach tonight. And its not working. The green wire is in the MSD 6al Tach Output slot, Red is in fuse #11(radio), Black grounded, and White into fuse #13 (Illumination). The needle just sits on the shift point and won't move. Does this sound like I need a tach adapter or need to do some rewiring?

[Blown 5.0]

Running off the msd you shouldnt need a adapter. I would check ground and be sure i have ground, most of the stuff in and around the dash is plastic, may be nessary to just run a temp. wire from ground and hot battery just for checking purpurse. does the needle move any at all? Does key on and key off make any differnce? May have a bad tach. Hope this helps

[EZMachN]

I have the ground ran through my firewall onto the fenderwell. Once cranked I can turn the needle with the shift set knob, but it won't go past 1k rpms, it stops there

[EZMachN]

It is getting power from the key on, b/c once key is on(not cranked) it will move to the previous shift point. Once cranked it drops to 0 then shoots to 5k(shift light point) and sit there. Which makes me think either need adapter or broken tach

[Blown 5.0]

Broken Tach

[EZMachN]

Bought a $185 Auto Meter Sport Compact today. Still don't work :metal:

I'm thinking its the damn MSD?

[04 Mach1]

Hook the tach signal wire to the neg side of the coil that way you know you have a signal. The tach output on the msd 6al might be burntup.

[EZMachN]

Yea, I ran a voltometer(sp?) to the tach output and was getting negative reading. And you can't run the tach to negative coil with MSD b/c it will fry it up and void warranty.

[Italian LX]

Yea, I ran a voltometer(sp?) to the tach output and was getting negative reading.
The Tach output should be an AC signal.

And you can't run the tach to negative coil with MSD b/c it will fry it up and void warranty.
For testing purposes, you can remove the MSD box and then do what Mark suggested.

[EZMachN]

The Tach output should be an AC signal.


I'm new to voltmeter stuff. But guy at Auto meter said I should be getting a 1.5 to 5volts from my Tach Output. Would that be -1.5 to -5?

[TheJeanyus]

If you hook up the voltmeter backwards, the signal will be negative. If you had hooked it up the other way, it should have been positive. Like Brian said, though, it should be AC, not DC, meaning the polarity would alternate.

[Italian LX]

If you hook up the voltmeter backwards, the signal will be negative.
:werd:

Like Brian said, though, it should be AC, not DC, meaning the polarity would alternate.
Actually, the polarity might not alternate, but it still should be some sort of alternating square wave.

[slvrbullit]

Did you by the plug and play harness for the MSD or did you splice the wires into the factory harness? If I remember correctly, the white wire from the MSD is the trigger wire for the tach signal that picks up off the trigger wire for the ECC. If there is a good connection there then you may need to take the MSD back to the seller and swap it out for a new one. If you got it at SECO they should be able to test it for you. I know they did on mine when the MSD went bad and was sparking when it wanted to.

[EZMachN]

It was in the car when I got it. I'll check the white wire when I get home in a couple hours.