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racer88

260z tach resistor

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racer88    0

Hi Everyone

I have a 74 260 that the PO for reasons unknow has removed the resistor that is in the wiring that supplies the signal to the tach from the coil ( the blue wire). I have searched every where for the resistance value of that resistor with no luck. Does any one know what it is? Any help would be great. I have totally upgraded the wiring, hei ign, gm alt.,maxi fuses everything on relays, but i would really like to keep the stock style tach.

Thanks in advance

Bob morris :icon46:

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Zmanco    13

Is your tach one of the 70-73 current triggered types, or one of the later 75-78 voltage triggered tachs? If it's current triggered, there is no resistor. I don't know for sure for the voltage triggered, but I'll say that I just put one in my 73 without a resistor and it's working great.

 

Perhaps you are referring to the resistor that's mounted near the coil in the engine compartment? That one is only to protect the points for non-electronic ignitions and is not needed once you install an HEI ignition. It is not needed for the tach to operate properly.

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lowrider    11

I actually know this one!!!!

Zmanco, like the 75-78 the 260z's tach is voltage triggered. There is a resistor in the line running off of the negative side of the coil. The resistor is housed in a fuseable link case in the passenger side footwell.

 

Racer88, the resistor is a 2.2k ohm resistor! just got finished replacing mine for one out of a 280zx.

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racer88    0

yes it is the one under the dash. its purpose it to reduce the voltage of the signal to the tach. My car is an early 260 but it is my understanding that it has the same tach as the later cars. The 2.2k ohm number was what I was missing. Thanks everyone I will pick one up tonight and give it a try

This site is such a wonderfull resource

Thanks Bob

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lowrider    11
Interesting, it's probably there to help with potential noise issues. I've been running without it for a few months now with no issues. Still, not a big deal to add it - less than $1 at Radio Shack.

Im sure its not that big of a deal either, im running a sunpro tach and it works both with and without the resistor.

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Tony D    143

It is a common wire, and the added resistance in the line acts as a 'check valve' during some periods of operation.

 

I removed mine, reinstalled, and eventually removed it to no difference in operation of my Autometer Tach. Mine now resides in the glove box...

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racer88    0

I finally got back to the zcar wiring. I hooked up the tach without the resistor. I ran the car with a Snap On tach and dwell meter hooked up and the reading on both tachs were the same. I think the best place for the resistor is left on the bench or in the tool box. One less thing to burn out.

Thanks

Bob

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Dat260    15

I have the same problem with a jumping tach. I change the resistor in the passanger foot well like suggested above and still have the same problem. Iam thinking maybe the coil since it seems its the original one but the car runs fine so I do not know what else to do. My car is an early 260Z 5/74.

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Dat260    15
Posted (edited)

Hi Guys,

I 'am bringing back this old topic since I 'am still trying to figure out my problem. My car is a 260Z 5/74. My tach started to jump all over for a while and eventually got stuck at 8k and stayed there.I've replaced my coil, I've removed the resistor at the foot well on the passenger side, I also replaced it with a 2.20ohm 1/4W, made a direct connection and still not working. I've dismantle my tach and sent it to be checked. The technician showed me that the tach works. He plugged it to a small machine and showed me how gradually the needle moves, costed me $50.  I've traced the blue wire; goes from the coil and "T" off to the ignition box then goes to one side of resistor. Than, from the other side of resistor to the tach. I've used a test light and there is power at all ends except from the resistor to the tach. Can the problem be my ignition box?

 

Would greatly appreciate some input.

BTW, Iam glad this site is still up, Thks Dan.

Edited by Dat260

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cgsheen    15

Is your engine missing as well?  (as badly as the Tach is jumping around?)  The blue wire from the electronic ignition module is the "signal to fire" to the coil.  If the electronic ignition module was faulty in that way, I'd expect the spark from the coil to be erratic as well. If the Tach is known to be good and the engine runs smoothly, I'd suspect the wiring / connections between the electronic ignition and the tach.  It wouldn't be that difficult to run entirely new wiring from the electronic ignition module to both the coil and the Tach - it's a simple circuit.

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