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Showing my ignorance about tachometer
https://www.slantsix.org/forum/viewtopic.php?t=18974		 Page 1 of 1
Author:  '74 Sport [ Wed Aug 02, 2006 1:05 pm ]
Post subject:  Showing my ignorance about tachometer
OK, here's the deal, and don't make fun of me, I don't understand how this tachometer works. On the back of the case, instructions say to connect the red lead to the "positive terminal of the distributor" and the black lead to a ground. I don't see anywhere on the electronic distributor to connect a lead wire clip.

Be nice,
Jerry
Author:  Reed [ Wed Aug 02, 2006 1:15 pm ]
Post subject: 
Every tach I have ever dealt with has three wires- ground, (-) coil terminal, (+) feed for illumination. Never heard of a lead for the distributor (+) line before.
Author:  Super6 [ Wed Aug 02, 2006 1:59 pm ]
Post subject: 
Quote:
Every tach I have ever dealt with has three wires- ground, (-) coil terminal, (+) feed for illumination. Never heard of a lead for the distributor (+) line before.
All the tachs I have seen have 4 wires....

Aftermarket tach wire colors are usually:

Black: Ground
Red: Ignition Switched Power
White: Illumination
Green: Trigger wire (to coil negative terminal, or tach output of Ignitions like MSD or Jacobs)

Is this a factory tach, or an aftermarket add-on?
Author:  Reed [ Wed Aug 02, 2006 2:35 pm ]
Post subject: 
Oh yeah, I forgot the (+) switched feed. Sorry.

I suppose you could run the switch (+) feed to the (+) coil terminal...
Author:  '74 Sport [ Wed Aug 02, 2006 3:39 pm ]
Post subject: 
Sorry, guess I didn't make myself clear. This is a hand held tach / dwell meter. It only has the two wires.

Jerry
Author:  DusterIdiot [ Wed Aug 02, 2006 3:55 pm ]
Post subject:  Easy...
Green wire = negative side of the coil
Black wire = ground
Author:  '74 Sport [ Wed Aug 02, 2006 9:03 pm ]
Post subject: 
"1. Connect red clip to primary terminal of distributor and black clip to ground. Reverse for positive ground."

That's the first line of the instructions printed on the back of this tester.
It is a Model T-111 made by KAL-EQUIP CO. of Otsego, MI. It has one switch to select TACH, DWELL, or POINT RESISTANCE. Another switch to choose between 6-cylinder or 8-cylinder. The last switch selects HI or LO rpm scales.

DI, are you thinking the red alligator clip goes to the coil, rather than the distributor? If so, does it go to the negative side, and how do I tell which one that is?

Jerry
Author:  DusterIdiot [ Wed Aug 02, 2006 10:27 pm ]
Post subject:  Try it one way...
My tach/dwell has a green and black clip....the old one my grandfather had was a red and black clip...red went to the - side of the coil and the black went to the ground... (if it doesn't make a reading you can always switch them....)


good luck,

-D.Idiot
Author:  '74 Sport [ Wed Aug 02, 2006 10:39 pm ]
Post subject: 
Your grandfather, huh? That's probably the case here. I got this tester at a pawn shop for $10. My father-in-law showed me one just like it in his shop, but it doesn't work (which begs the question... why keep it?) I'll give it a try tomorrow.

Thanks,
Jerry
Author:  emsvitil [ Wed Aug 02, 2006 11:29 pm ]
Post subject: 
Quote:
Your grandfather, huh? That's probably the case here. I got this tester at a pawn shop for $10. My father-in-law showed me one just like it in his shop, but it doesn't work (which begs the question... why keep it?) I'll give it a try tomorrow.

Thanks,
Jerry

Maybe it needs a new battery................
Author:  dakight [ Thu Aug 03, 2006 5:19 am ]
Post subject: 
Quote:
Quote:
Your grandfather, huh? That's probably the case here. I got this tester at a pawn shop for $10. My father-in-law showed me one just like it in his shop, but it doesn't work (which begs the question... why keep it?) I'll give it a try tomorrow.

Thanks,
Jerry

Maybe it needs a new battery................
I've never seen a tach/dwell with a battery. Mine has 2 leads, green and black, and a switch for RPM/Dwell. It also has dual scales, 8cyl graduations in white and 6 cyl in red along with a note on the face to double the 8 cyl reading for 4 cyl engines. WhenI had cars that ran on points I used it constantly but I've had little need for it in about 20 years. I'm sure I'll use the Tach function when the Valiant is running but probably not the Dwell function.
Author:  emsvitil [ Thu Aug 03, 2006 5:31 am ]
Post subject: 
Quote:
Quote:
Quote:
Your grandfather, huh? That's probably the case here. I got this tester at a pawn shop for $10. My father-in-law showed me one just like it in his shop, but it doesn't work (which begs the question... why keep it?) I'll give it a try tomorrow.

Thanks,
Jerry

Maybe it needs a new battery................
I've never seen a tach/dwell with a battery. Mine has 2 leads, green and black, and a switch for RPM/Dwell. It also has dual scales, 8cyl graduations in white and 6 cyl in red along with a note on the face to double the 8 cyl reading for 4 cyl engines. WhenI had cars that ran on points I used it constantly but I've had little need for it in about 20 years. I'm sure I'll use the Tach function when the Valiant is running but probably not the Dwell function.
All my tach/dwell meters have had a battery........... (the older analog versions)

I know the dwell function needs a power source because the meter figures out dwell by how much time current can flow to ground vs how much time it can't.

Not sure about the tach function needing a battery or not.......
Author:  dakight [ Thu Aug 03, 2006 5:51 am ]
Post subject: 
I'm not saying they don't exist... obviosly if you have one or more with batteries they do, just saying I've never seen one. All that I have used have just had 2 leads, ground and coil and the one I have now, which I've had at least 25 years, worked as late as 4 years ago for the tach function. I've had no need to measure dwell in many years. The last car I had with points was the 69 Dart which I replaced in about '82 with a '78 Aspen. I suppose it's possible that the meter has a battery hidden away inside the case but there is no external compartment for one, only 3 screws to open the entire case.

Well, curiosity got the better of me and I opened the case... as I thought, no battery.
Author:  KBB_of_TMC [ Thu Aug 03, 2006 10:05 am ]
Post subject: 
The 2 wire tach/dwell draw their current to run the meter from the (-)coil; and when they go bad they can disable the ignition.

Many 50+ year old precision devices used a mercury battery as a voltage reference, not for power, though I've never seen a tach/dwell use one. Any tach/dwell that is also intended to be used as an ohmmeter too would probably have its own battery.

Most modern tachs use a NE555 or similar as a monostable and draw only a insignificant current from the ignition.

The Mopar factory tachs I've fixed don't use a monostable, but rather charge up a capacitor and discharge it through the meter - note the meter's (+) connection goes to ground. A sketch of one from the 70s: http://www.tidewatermoparclub.com/TECH/tach.jpg
Author:  Avenger2040 [ Thu Aug 03, 2006 11:23 am ]
Post subject: 
Problem here with original Mopar Hood tach, worked well with points ignition, but when switched to electronic it don´t mark well, got a red, black and green with a black line wire, currently my electric mechanic make it work coneccting the red wire to negative coil terminal, green is to ballact resistor and the black is just there doing nothing.

Mechanics that have fixed mopars with hood tachs says that this one works well with 6 & 8 cyl and points & EI, there is no visible switch in the tach, any idea? also tach light don´t work, I know the bulb is not broken, I can a see a very dim orange light.

If it got a switch meaby is inside, but I don´t know how to open it. Another thing, don´t know from wich year the tach is, my guess is from 72-74 Slant 6 Duster. I shall try connecting the red wire to electronic ignition box in the wire that goes to negative coil terminal.
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