tachometer installation

M

Motorhead6

Senior Member
Have a tach with only 2 wires; red and black. How is this supposed to be wired? Am I correct in assuming red is 12v and the black goes to - coil post? It is a big block ford with Pertronix III.
 
Motörhead.......one would be ground assuming the black one. I can't remember where the other goes to on mine !
 
Can't see how that would work.
All the tach's I've seen and wired had 4 wires. Red: power source 12 volt ignition, Black: ground, White: dash light, Green: distributor side of coil or tach connection if HEI type ignition.
I would think you should have minimum of 3 wires. If only 2 then one would have to be a signal wire but I don't know which in this case.

Dave
 
Dave Covey said:
Can't see how that would work.
All the tach's I've seen and wired had 4 wires. Red: power source 12 volt ignition, Black: ground, White: dash light, Green: distributor side of coil or tach connection if HEI type ignition.
I would think you should have minimum of 3 wires. If only 2 then one would have to be a signal wire but I don't know which in this case.

Dave
Click to expand...
Those were my thoughts too. I'm equally confused.
Maybe the red wire is for the distributor side of the coil and the black is ground :confused:
If the tach housing can be opened up, check inside for missing wires that used to lead outside the housing that may have broken off.
 
Motorhead6 said:
Have a tach with only 2 wires; red and black. How is this supposed to be wired? Am I correct in assuming red is 12v and the black goes to - coil post? It is a big block ford with Pertronix III.
Click to expand...

Most tach/dwell meters have only two wires, including two I have, a Sun and an Accurate. For negative ground polarity, Red goes to the distributor side of the coil, Black goes to ground.
 
V8 Bob said:
Most tach/dwell meters have only two wires, including two I have, a Sun and an Accurate. For negative ground polarity, Red goes to the distributor side of the coil, Black goes to ground.
Click to expand...
Well yes they do.... "More coffee!" :o
 
I have a Ford tach that I bought over the counter at the dealer and it only has 2 wires. It runs in series with the power wire to the coil. I think a lot of the 60's in dash Ford tachs did that, like Mustangs and Fairlanes. Be best to try and find the mfg name. Mine was supplied to Ford by Faria. I've read that some of the electronic type ignitions can burn them out.
 
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