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Discussion Starter · #1 ·
I'm having some issues with the tachometer I just tied to hook up today. There was the 4 wires coming off of it, +, ground, illumination and the one that goes to the coil. First off the light inside the tach didn't work, no biggie. I go to start the truck, it starts up , but the tach doesn't work. I grabbed my test light and I have power going to the tach. The wire going to the coil is sending juice to it, but when i put the test light on it, it lit up and flashed with the rpms while the engine died? Not to sure if I hooked it up wrong or what any ideas for things to check?
 

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ok once again. green goes to negative side of coil, red goes to power supply, black goes to body ground, white goes to headlight/switched power for illumination of tachometer.

eric
 

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took me a while to figure that out too. The instructions that came with mine said to install it on the positive side of the coil...I thought it was broke and was about to replace it when I went ahead and switched it over to the negative terminal...
 

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Another possibility--Is it a 4,6,8 cylinder universal tach? If it is, check the 4-6-8 selector switch--it may be stuck in a middle position instead of selecting a # of cylinders.

-SM

 

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Discussion Starter · #7 ·
No idea what kind of tach it is, just one that my dad had laying around so I put it in. I found out today on my way home from work that it works, but only if the lights are turned on, so I got the power wire and illumination wire mixed up. 2 of the wires coming off of the tach are red, ones black, and another orange.

Also on another note, things that quit working for some reason started working again after I hooked up this tach. One of my turn signal lights inside the gauge cluster wasn't working until i hooked this up for some reason or anotherit started working, also, when i would start it up, it would not go onto the fast idle cam on the carb. Even after sitting for about 7 hours this evening while I was at work. It always starts out on the fast idle cam until I kick it down. At first I thought that it was going to die because it didn't. Wierd. ???
 

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Some tachs go to negative and some to positive. I have also had tachs that wont work on either.
 

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ramit87 said:
Some tachs go to negative and some to positive. I have also had tachs that wont work on either.
Are your sure???? I'm not sure that it could work on the positive, as it just has constant voltage that gives no indication of cylinders fireing, where as the negative switches between open and ground for every fireing of the coil.
Unless there is some method I have not seen yet? ???
 

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KThaxton said:
ramit87 said:
Some tachs go to negative and some to positive. I have also had tachs that wont work on either.
Are your sure???? I'm not sure that it could work on the positive, as it just has constant voltage that gives no indication of cylinders fireing, where as the negative switches between open and ground for every fireing of the coil.
Unless there is some method I have not seen yet? ???
I had a 71 Ford F100. I had to hook up the tack on the positive side of the coil. It would not work on the negative. I had taken the tach out of a nissan truck I had and hooked it up to the coil on the negative side just like I had it wired in the Nissan. It did not work-I moved it to the positive side and it worked. I know with the MSD ignition it will not work when hooked to the coil-period. I used the tach port on the MSD box to get the tach to work.
 

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Discussion Starter · #11 ·
I changed the two wires around and it works fine now. Just to let you guys know what wires were what, There were the 4 wires, 2 red, 1 black and 1 orange. Well one of the red ones(was the longest wire) went to the coil, the other red one went to the lights, the black to ground and the orange to the power. Kinda messed up.
 
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