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Wiring problems Tachometer Mustang -73


nursieee
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To accurately measure each component individually requires removing each component from the circuit and test it in accordance with what type of device it is. In the picture I see the a transformer, 2 diodes, a resistor and 2 capacitors, each of which are tested differently. The way to test them in the circuit is to input a signal and then follow the signal through the circuits from beginning to end, and know what the expected readings are after each device. In this case the signal would have to be a pulsing signal, 8 volts loaded through a resistor and unloaded, just like the points load and unload the ignition coil.

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“If you can't explain it simply, you don't understand it well enough.”

--Albert Einstein

 

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  • 2 weeks later...

Just curious about what kind of upgrade you are bought, what it is supposed to do?

Just some new hardware like ignition coil, circuitboard, volt regulator.... just to see if the tach probs had something to do with them....

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  • 1 year later...

So now im back on track, it begins again. Some more stupid questions. I gave up my old tach and bought a new one from tachman, that im about to install.

So this is my first question on the picture i point at a device on the wiring schedual is that the one thas called solenoid? On the picture the device that is attached to the blu wire?IMG_20210403_200957.thumb.jpg.6ace3047c5003ac0d97c28c12884e2c5.jpg

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Yes, that is the starter solenoid, that Ford called a starter motor relay, because that is what a starter solenoid is, a relay.

Edited by Don C
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“If you can't explain it simply, you don't understand it well enough.”

--Albert Einstein

 

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My first time reading this post. 

In 1971, Ford changed the wire color for the "pink" resistor wire to a red/orange or red/green resistor wire. 

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Let me check your shorts!

http://midlifeharness.com

cactus.jpg.92e5d9d8700abc0ed60c8ccb3426248e.jpg

 

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Posted (edited)

More questions.

Nr 1 is wired from ignition coil, same place where the ignition coil goes to the distributor, to the tach.

Nr 2 is where i think im gonna place the red cable from the tach. Can i connect it there or do i have to connect it before the bracket, meaning do have to cut the cable?

Nr 3 I dont find the white device that is connected before the ignition coil on the wiring diagram for my mustang? What is it, why is it there?

 

Inkedignition coil_LI.jpg

tach wiring.jpg

Edited by nursieee
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You are using one of my wiring diagrams (Rocketman) to install a Tachman tach?  Interesting.

The jumper I refer to in my instructions is to connect the two wires in the OEM tach connector to complete the primary circuit from ignition switch to coil +.  I would have sent the original tach pigtail back so that you can use it to make the jumper.

 

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Bob

 

Tachs, Voltmeters, Headlight kits, Wiper delays and more at

http://www.rccinnovations.com/Images/smlogo.jpg

Rocketman's Classic Cougar (and Mustang) Innovations, LLC

 

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Hi

Yes i bought the tach from you about a year ago didnt have any time to work with it until now, but now im on it again.

I can do that jumper myself with a wire no problem. Since i live in Sweden it takes long time to get things from the USA. Ill get back on how it works.

Now the problem is that white device that is connected before the ignition coil since i dont find it on the original wire diagram? Should i connect the tach to that one or should I connect it direct on the ignition coil ?

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That white device is an external ballast resistor.  Chances are it was installed for 1 of 2 reasons:

1.  The original resistor wire failed.

2.  They wanted to get 12V for a Pertronix Ignitor or other device, but still needed reduced voltage to the stock coil.

If you are running a Pertonix Ignitor you can power it off the ballast resistor input side (the stud not wired to the coil), and ground it to the block. Note that when using the external ballast resistor you need to run a new non ballasted wire from the ignition switch to the resistor.

(in the future, please try not to give tachman credit for my work) :classic_wink:

 

 

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Bob

 

Tachs, Voltmeters, Headlight kits, Wiper delays and more at

http://www.rccinnovations.com/Images/smlogo.jpg

Rocketman's Classic Cougar (and Mustang) Innovations, LLC

 

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Hi

Sorry Rktman, you have to think of me like a sligthly retarded Swede, I will give you credit for your work in the future =)

I still dont really understand how to connect the wire.

By the way it says on my ignition coil that it is to be used with external resistor saw it on the picture, so of course thats why it is there.

It seems like i dont have a pertronix ignitor. So no im still a bit confused. If i follow your wiring Rktman, i conncet the black cable to the block(ground) and the green cable to - on the ignition coil.

But where am i to attach the RED ? on the resistor input (nr 2 in the pic) or direct on the ignition coil + according to your wiring ?

/Conny

 

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If you don't have a Pertronix, what kind of ignition do you have? It's important to know what you have to be able to get the wiring correct. Maybe take the cap off the distributor and take a picture of it.

 

 

“If you can't explain it simply, you don't understand it well enough.”

--Albert Einstein

 

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1 hour ago, nursieee said:

Hi

Sorry Rktman, you have to think of me like a sligthly retarded Swede, I will give you credit for your work in the future =)

I still dont really understand how to connect the wire.

By the way it says on my ignition coil that it is to be used with external resistor saw it on the picture, so of course thats why it is there.

It seems like i dont have a pertronix ignitor. So no im still a bit confused. If i follow your wiring Rktman, i conncet the black cable to the block(ground) and the green cable to - on the ignition coil.

But where am i to attach the RED ? on the resistor input (nr 2 in the pic) or direct on the ignition coil + according to your wiring ?

/Conny

 

My tach wires like so:

 

Black to ground - you can ground it to the back of the cluster.

Red to switched power - you should be able to connect it to the jumper you put on the original tach plug.

Green to - side of coil.

 

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Bob

 

Tachs, Voltmeters, Headlight kits, Wiper delays and more at

http://www.rccinnovations.com/Images/smlogo.jpg

Rocketman's Classic Cougar (and Mustang) Innovations, LLC

 

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1 hour ago, Don C said:

If you don't have a Pertronix, what kind of ignition do you have? It's important to know what you have to be able to get the wiring correct. Maybe take the cap off the distributor and take a picture of it.

And it says motorcraft 12127 on the backside of it. Do you get something out of the pic?

1617656373563.jpg

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You have a stock points ignition. Follow Bob's (Rocketman) instructions on how to connect it.

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“If you can't explain it simply, you don't understand it well enough.”

--Albert Einstein

 

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"You have a stock points ignition. Follow Bob's (Rocketman) instructions on how to connect it. "

You mean Tachman's instructions?    JUST KIDDING, BOB!

Bob is one of the few people I trust completely with wiring instructions and knowhow.  He's the bomb!

Edited by midlife

Let me check your shorts!

http://midlifeharness.com

cactus.jpg.92e5d9d8700abc0ed60c8ccb3426248e.jpg

 

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Posted (edited)

Thank you all for all the help. I managed to start my mustang today, it was long since i heard it. And the tach did work.

So i started a new thread about next problem.

But now there is hope for my mustang to get som air this summer.

 

Edited by nursieee
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Sorry got it wrong the tach didnt work think it just was vibrations from the car, had no gas so couldnt test it properly.

So it is connected correct as rcktman said. Back to ground. Green from distside of ignition coil, there i measure only 8 volt and when you press gaspedal it gives 20 volt but still the tach isnt moving. The redwire gives 12 v when turning key.

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Check that the coil is not wired backwards. I have seen many coils with + (IGN) and - (DIST) posts wired wrong.  The car will run that way, but not that well.

Easy way to make sure:

Take the wires off the coil.
Turn on key switch.
Wire with voltage goes to positive + (IGN) side of coil.
Wire coming from distributor with no voltage goes to negative - (DIST) side of coil.
 

Edit:  20V?  Wow!

 

Edited by TheRktmn

Bob

 

Tachs, Voltmeters, Headlight kits, Wiper delays and more at

http://www.rccinnovations.com/Images/smlogo.jpg

Rocketman's Classic Cougar (and Mustang) Innovations, LLC

 

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