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620 Tach Wiring


g-mam

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Trying to figure out how to wire this tach into my 620.

 

  1. Goes to Ground
  2. Goes to + 12v when ignition is on
  3. Goes to dash lights
  4. Goes to Neg. Coil side
  5. NO CLUE ! :confused:

 

tach.jpg

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That's an induction tach. The wire from the points to the (-) coil post has to go through that loop. That particular tach is wired in series with the coil. Otherwords, the stock points-to-coil wire is disconnected, and the tach takes the place (with longer wires of course). #5 goes to the dist, #4 goes to the coil, though it doesn't really matter which direction since it's inductive.

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That's an induction tach. The wire from the points to the (-) coil post has to go through that loop. That particular tach is wired in series with the coil. Otherwords, the stock points-to-coil wire is disconnected, and the tach takes the place (with longer wires of course). #5 goes to the dist, #4 goes to the coil, though it doesn't really matter which direction since it's inductive.

 

I wonder if this will still work with my Igniter sytem? I eliminated the points? It still has a wire to the - side of the coil.

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It uses induction wiring, the coil + wire feeds that loop. All the Datsun 1200 tachometers are wired like that.

 

The 620 tachometer I have (otherwise look like a 1200 tach) is conventional wiring, no loop. Instead you connect it to coil -. Or electronic ignition Blue wire.

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They didn't have wiring in the dash for a tach until '76 (maybe '75), when the factory option/dealer option tachs became a plug-in deal, elimitanting the wire loop. The plug-in tachs wired in parallel. Quite different externally.

 

Dave, you sure it's the coil (+) wire? That's simply drop-resistored 12V hot off the ignition. Though I suspect it doesn't matter as the current through both is the same.

Edited by datsunaholic
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I jury rigged the tach today to test and it works fine.

 

Now, can SOMEONE TELL ME HOW TO REMOVE THE INSTRUMENT PANEL :confused:

 

I have removed the three screws in each housing, and I found one under the dash, but the right side is just solid.

 

I unscrewed the Wiper control (and can't figure out how to get that knob off). I removed the heater knobs. The radio is free, I just can't figure it out. Removed the ashtray mount, nothing there. It seems solid near the dimmer for the dash lights.

 

I looked under the dash for an hour, pulling on it trying to figure out how to get it out. There must be a secret somewhere.

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The wiper switch and the cigarette lighter hold in the right side. The wiper knob pulls out but its attached to a fiberoptic. The fiberoptic has to be unhooked, I had to cut mine near the box that lights it.

Edited by Suspect
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I have the wiper nut loose (still can't get the knob off).

 

How is the Cig lighter holding it in? I can't see it, will have to use the braille method.

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take needle nose plyers to hold the shaft for the wiper then push knob in and turn.

 

Cig lighter has a hollow barrell shape on the back side and unscrews, remove the wire first then put a finger inside where lighter goes to hold it in place as you unscrew the barrell. gl

Edited by 420n620
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  • 1 year later...

I know this is an ancient thread,but I'm installing a tach in my 73 620 ,and my tach is different. I'm not sure if it's a 1200 or what. If I'm reading this right the black/white wire on the left (maybe blue/white?)goes to the coil - side?

 

tach.jpg

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How you wire it Depends. Do you have that same Tachometer or one with different wiring?

 

ONE without a loop wire?

_thPdr_0312a.jpg

you connect the B/W wire to coil - (coil neg)

 

OR ONE with a loop wire?

18920.jpg

The wire loop goes into the coil circuit.

* What Datsun did was splice the loop into the dash harness coil feed wire.

* or you could remove the wire from the Ballast Resistor, reroute it into the cabin and connect it to one end of the loop (#4 in the photo). Then run the other end of the loop (#5) back to the resistor. As DH said you could probably do same for COIL NEG wire (maybe easier as it doesn't matter about the resistor/lack of resistor) but the factory wiring was on the COIL POS side. NOTE: If you have converted to EI and removed the Ballast Resistor, do it for Coil + wire.

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OK, your is a regular 620 tachometer:

tach.jpg

This is wired is just like a typical aftermarket tachometer only three wires are required.

* BLACK wire: ground, can connect it to the metal dash frame

* YELLOW/red wire: 12V, wire to IGN + somewhere under the dash

* BLACK/white wire: connect to COIL NEG post

 

The lamps don't need to be connected for the tach to work. But usually they are connected to some BLUE wire under the dash.

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  • 4 months later...

How you wire it Depends. Do you have that same Tachometer or one with different wiring?

 

ONE without a loop wire?

_thPdr_0312a.jpg

you connect the B/W wire to coil - (coil neg)

 

OR ONE with a loop wire?

18920.jpg

The wire loop goes into the coil circuit.

* What Datsun did was splice the loop into the dash harness coil feed wire.

* or you could remove the wire from the Ballast Resistor, reroute it into the cabin and connect it to one end of the loop (#4 in the photo). Then run the other end of the loop (#5) back to the resistor. As DH said you could probably do same for COIL NEG wire (maybe easier as it doesn't matter about the resistor/lack of resistor) but the factory wiring was on the COIL POS side. NOTE: If you have converted to EI and removed the Ballast Resistor, do it for Coil + wire.

 

Hey You can Drawing for Loop wire Feature Thank you evrry much

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