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1973 Datsun 620, now it b a tach question


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I am installing a complete dash out of a 73 into my 1976 620. In inspecting the wiring of the dash I was puzzled by two blue and white wires that come to a plug with a sensor that has blue wires to it that are fried. In my googaling I find it to be a "Temp Sens SW". What is it's purpose?

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I have an induction tach...Understand that Nissan had it ran off the coil positive side....could I run the induction wire to the temp send harness?

 

 

20171230_184003.jpg

 

Huge shout out to the wife, she is the master dash rebuilder. On the tach, I had a stock clock...found a 180b tachometer overseas for cheap....put the tach in the clock casing...looks okay

....I think.

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I am installing a complete dash out of a 73 into my 1976 620. In inspecting the wiring of the dash I was puzzled by two blue and white wires that come to a plug with a sensor that has blue wires to it that are fried. In my googaling I find it to be a "Temp Sens SW". What is it's purpose?

 

Yes, part of the emissions system for switching the dual points on or off. It senses the cab temperature above 50F and with a throttle switch (above idle position) works the relay that turns the dual points ON which retards the ignition timing by about 7 degrees.

 

Why the inside of the cab temperature? Beats me. You would think  the temp of the air going into the carb would be better or the temp of the warming up engine.

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Mike, any idea on the Tach?

 

If an induction tach, you have to run a wire from the coil negative terminal through the tach and back to the distributor points. The tach must be wired in line.

 

cZzxS4u.jpg See the 4/5 wires? It just loops through that sensor. One goes to coil negative, the other to the distributor points. If it doesn't work, reverse the wires.

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Understood Mike...Question is could I run it through the temperature sensor harness,

The harness goes to the + side of the coil. If I understood correctly, it was mentioned in another thread that Nissan originally ran the induction loop through the positive side of the coil.

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The temp sensor works the temp gauge, can't run a tach signal on it at the same time.

 

 If you have an inductive tach wire it the way I posted and it will work. To prove it, take the tach to the engine and take the coil negative wire off and place the tach between it and the coil so it is in-line.

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This thing...

20171202_134438.jpg

I've been wondering to.... I have a 72 521... I think i disconnected everthing else it was connected to....

 

I think it has something to do with the dual points.... I think it runs through that and full throttle switch, and to the coil or dizzy...

 

 

WHAT?, reread the thread MIke.I am referring to the Temp sensor shown above.

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I wouldn't. Ones side goes to the fuse, the other to the carb switch.

 

Get about 10 feet of wire and run it through the loop in the tach and the other two ends out through the firewall to the coil and distributor. This is what I did..

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I no longer am able to drive, so I am building this to sell. With this in mind I am trying hard to not have anything look jury rigged. Thus no bare wires thru the firewall. I have worked really hard on the 620..everything that affects the drivability has been addressed...

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