ConcoursMustang Forums
1st Generation 1964 1/2 - 1973 - Questions & general discussions that apply to a specific year => 1969 Mustang => Topic started by: STAUBY38 on April 04, 2025, 12:00:48 PM
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I have read several different Tach issues online but not one that describes my issue and I wanted to see if anyone could assist me with figuring this one out. Here is my dilemma. 69 Mach Original Tach car. New wiring harnesses. Pertronix system. Tach was working ok then became intermittent. Figured it was the Tach starting to go bad. Sent to the Tach guy. Rebuilt to original 2 wire and returned to me. Installed in the car. Needle doesn't move when running. Has power because car starts. Coil is wired with Peritronix red on Battery Side and Black wire on Ground per directions. Tach wire harness from firewall to coil which is red/,green wire is also on the battery side of coil according to the wiring diagram. I spoke to Peritronix Tech and they said it should work with the original wiring set up from Ford. Spoke to Tach Guy who wasn't sure if it needed to be made a 3 wire or not. Questions:
Where does the Tach get its Signal from ?
What am I missing here?
Is there some type of power or ground through the cluster that controls the Tach?
I am also having issues where the turn signals flash but they do not light up in the cluster( Unknown if related due to some issue with the circuit board)
Is there a specific way the tach has to be installed in the cluster so its grounded?
Is there a way to test the tach here to make sure its not that?
At this point I am not sure if its the Tach or wiring or a power/ ground issue since they don't work like a traditional tach.
Any assistance in trouble shooting would be appreciated.
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Which Pertronix do you have? I know Pertronix I works with the stock tach but could be issues with either a II or a III (definitely with the III I think).
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It just the basic 1281 model. Like I said, it was working prior with Pertronox installed but after rebuild its not at all....
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Did you explain to the tach guy you were adding pertronix?
The original tach works on somewhere around 6 volts, the pertronix works on 12 volts. put constant (running)12 volts through the tach and you'll fry the tach. I just had my tach modified so that the original wiring works with the pertronix, just need to add a 12 volt feed from ignition to the tach. (I don't know what my gauge guy did internally)
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The tach worked with Pertronix before the rebuild and the Pertronix tech said it should work with the current wiring without modifications so you see my issue that no one can give me a direct answer on why its not working. The Tachman told me he can convert to a 3 wire which could address this but no one is sure. Worse comes to worse ill have to send it back to him and have it fully tested and then decide what to do next. Was hoping someone here had dealt with a similar issue and had info...