tachometers that need sending units?

[allstateguy]

Hi, the Studebaker content is that this aftermarket tach is IN my Lark.

It is an Allstate tach (built by ?) I've had it out of the cup, and it has the number 8 stamped on the back, nothing else. It has three wires. Black, red, and white. I figured out that the red wire runs the light (it lights up red, coincidence?)

If I put either the white or black to the distributor wire, it pegs it at 10000 rpm. Does this show that it needs a sender? Any ideas on what might work (Sun or ?)

Thanks!


JohnP, driving & reviving
an early Lark

[BobPalma]

John: The stamped "8" probably means it is calibrated for an 8 cylinder engine.

I'd attach the black wire to the (-) side of the coil and the white wire to a switched (i.e., ignition terminal on the back of the ignition switch) (+) source.

That way, the distributor triggering mechanism, if it is meant to operate without a sending unit, will receive an intermittent negative (ground) signal from the (-) side of the coil, and a (+) signal all the time from the (+) source, with which to "work."

If those connections force the needle down (backwards), switch them.

I'm a little suspicious of that red wire being for the lights. If the above connections don't work, I'd try running the red to the positive source. If the tach then works, you could run the white wire to a source for instrument lights.

I have no idea if any of that will work, so I accept no responsibility if it ruins the thing! But that's what I would try if it were mine. BP

[allstateguy]

Thanks Bob! I will give those combos a try this weekend. What you say makes sense. If those give me the same 10k results, I'll guess that it does need a sender (good luck sourcing an Allstate sender!)

JohnP, driving & reviving
an early Lark