Topic: 69 Mach 1 Tach Issue Help

[STAUBY38]

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.

[rockhouse66]

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).

[STAUBY38]

It just the basic 1281 model.  Like I said, it was working prior with Pertronox installed but after rebuild its not at all....

[Aussiemach]

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)

[STAUBY38]

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...

[midlife]

There are 2 main failure modes.  The first is that the input transformer goes bad, and that's when you're unable to get the engine to run.  The second failure mode is when the gauge guts goes bad: no movement but engine runs.
Send the tach back to Tachman..

[STAUBY38]

Thats the plan.   Thank you for the reply !

[Bob Gaines]

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.

Most people cure their PerTronix tach problems by running a seperate 12 V line (tap into ignition switch before tach or resistor wire) to the module PerTronix rather then using the coil power. If you ask Pertronics techs you will find that the PerTronix likes the full 12V better anyway . The power from the stock Ford wiring has a resistor wire so your stock coil doesn't get a full 12V. A full 12v will burn up your stock coil in short order. The Less than 12V resistor wire can work the PerTronix but may cause odd gremlins (symptom problems) that come and go to happen when you least expect them. I lost count how many times that solution cured similar problems. Best of luck in solving your problem.

[krelboyne]

This is a pretty slick device for installing Pertronix. Might take a bit of thinking to hide it on a concours car though.

https://desertclassicparts.com/product/ignition-power-relay-for-pertronix-ignitor-ipr-ford/

[Bob Gaines]

This is a pretty slick device for installing Pertronix. Might take a bit of thinking to hide it on a concours car though.

https://desertclassicparts.com/product/ignition-power-relay-for-pertronix-ignitor-ipr-ford/

I am not sure what the advantage of that highly visible set up would be over a direct wire from the ignition switch as I previously outlined? Maybe a fuse which can be easily added inline. A extra wire from the ignition can be easily concealed inside the tape engine gauge feed harness that carries the stock Ford coil feed and be extremely less visible too. At least it emphasizes the necessary full 12V that the PerTronix needs as I did.

[STAUBY38]

So Bob to get into this a bit more, If I add a wire, what wire coming out of the ignition do I tap into and then does that wire connect to the red Pertronix wire that is currently on the + side of the coil?  I assume you take the red wire off the coil, attach it to the one you ran from the ignition and then just have the harness wire that's on the + side of the coil now remain?  ( I know I shouldn't assume thus why I ask in detail)   This has been a process for sure and its starting to be not worth it. 

Thanks for the assistance..

Chad

[STAUBY38]

Scott   That's a pretty slick item.  I wish it was a little bit more concealed.   Will read into it a bit 

Thanks
Chad

[Bob Gaines]

So Bob to get into this a bit more, If I add a wire, what wire coming out of the ignition do I tap into and then does that wire connect to the red Pertronix wire that is currently on the + side of the coil?  I assume you take the red wire off the coil, attach it to the one you ran from the ignition and then just have the harness wire that's on the + side of the coil now remain?  ( I know I shouldn't assume thus why I ask in detail)   This has been a process for sure and its starting to be not worth it. 

Thanks for the assistance..

Chad

You want the same wire from the ignition switch that the tach plugs into.You want to tap in from the ignition because it is only powered when the key is on. You want to tap into power anywhere BEFORE where the tach bullet plug connection is .  You want to tap in before the tach connection because you do not want the tach in the Pertronix circuit . You take the + wire from the pertronix module and instead of the coil it connects to your ignition power wire.  You leave the Ford wire from the harness connected to the coil as stock .

[Bob Gaines]

Scott   That's a pretty slick item.  I wish it was a little bit more concealed.   Will read into it a bit 

Thanks
Chad

I wouldn't want it at the solenoid because you have more wires that are harder conceal at the starter solenoid compared to running a extra one inside the existing engine gauge feed harness. That is if besides keeping things more factory looking you want things looking neat and tidy.

[STAUBY38]

Makes sense Bob   I appreciate the input. I was told to take the red wire for the Pertronix off the coil and put it directly to the battery power to see if the tach then would work when starting. The car would start but the tach still didn't work.   That's kind of the same thing here isn't it with putting in a wire to the ignition 12v to make it work?   It was just a test doing it that way but it didn't work so it again sounds like the tach itself?



Chad