Who has pertonix with factory tach? Need some wiring help.

[PaleRider 12]

Had my tach rebuilt and now tach is showing only 1000 RPM max no matter how much gas I give it. I'm guessing it is because PO bypassed the resistor wire.

 

Would like to understand how it supposed to be hookedup. I'm guessing leave factory pink/red wire on + side of coil and run a new hot wire to red wire of pertronix but would like to hear what others have done:

 

1. What wires runs to + side of coil

2. What wire is run to red wire on pertroix and where did you tie into

3. What type of coil are you running

 

Any help would be appreciated.

 

thanks

[69RavenConv 286]

Your assumptions are correct.

 

The factory coil is a 6V and needs the pink resistor wire. The pink wire is designed to take 12V at the switch and drop it to 6V at the coil.

 

Some folks replace the factory coil with a 12V coil and ditch the pink wire altogether. Then you can hook up the Pertronix module and everything else that's 12V under the hood. Check to see if PO did this.

 

If you've got a factory coil and pink wire, you can get 12V for the Pertronix by splicing into the pink wire at the ignition switch, not the coil. (I hooked up my electric choke there as well). You can add an inline fuse to be safe.

 

On a factory tach car, I think the pink wire goes to the tach, then a red/green wire goes from the tach to the ign switch. In a non-tach car, the pink wire goes right to the ign switch. So for a tach car, you use the red/green at the ign switch instead of pink.

 

I don't have a tach, so double check this, but I would bet you a donut your hunch about the 6V/12V/pink wire issue is right.

[PaleRider 12]

69 Raven - you pretty much nailed it PO bypassed the pink, put in 12 volt coil. I think I will reconnect pink wire and drop a 6v coil back into the car and run like you said run a wire from igntion switch. I've got a couple questions though:

 

1) Where do I hood wire from igntion switch + side of coil or red wire on pertronix?

2) At start up I thought you are suppose to get 12 volts to coil but drop it to 6+ once car is running is that true? and what causes that to happen?

 

Thanks for your help.

[69RavenConv 286]

1) Where do I hood wire from igntion switch + side of coil or red wire on pertronix?

 

Hopefully, your harness is still intact. Re-connect the tach, ign switch and 6V coil back to the stock configuration. That means green/red from ign to tach, and pink wire to +coil. Disconnect PO's bypass wire to +coil

 

Now take that bypass wire that PO put to +coil, and hook it to red Pertronix. If PO did it right, it's connected to +12V at the ign switch.

 

Now everything should work.

 

If the Pertronix already had a good 12V at the red connection, skip the last step and just discard the bypass wire.

 

This site has wiring diagrams that should help:

http://www.themustangshop.com/resources.cfm

 

2) At start up I thought you are suppose to get 12 volts to coil but drop it to 6+ once car is running is that true? and what causes that to happen?

 

Yeah, technically, the voltage drop only happens when current is flowing thru the coil primary, +coil to -coil (Ohm's law). The grounding of the -coil terminal is controlled by the distributor electronics (either points or Pertronix). So yeah, all this theory only really works when the distributor is turning. I'll measure mine and see what everything reads when everything's turned off.

[69RavenConv 286]

Hey, maybe some cheesy ASCII art would help!

 

With Factory Tach (I think, never seen one)

 

Ign Sw

 

O---------Rd/gn------O [Tach] O---------Pink----------O +coil

|

|

-------------------------------------------------------O Pertronix Red

 

 

 

 

Without Tach

 

Ign Sw

 

O----------------------------Pink------------------O +coil

|

|

------------------------------------------------O Pertronix Red

 

 

 

Wrong!

 

O----------------------------Pink------------------O +coil ----O Pertronix Red

Ign Sw

Edited February 10, 2009 by 69RavenConv

[bnickel 10,004]

first off we need to know if the tach was rebuilt using the stock style 2 wire unit or if it was replaced with a 3 wire unit. the 3 wire unit hooks up like any aftermarket tach and the ignition is not dependant on teh tach working like the stock style 2 wire unit. if it was me i would have insisted on the on the 3 wire unit, because the engine will still run if the tach goes bad, not so with the the original 2 wire tach......ask me how i know that one.......nevermind i'll just tell you.

 

my old 70 cougar had a factory tach installed at one point and it had some kind of intermittent problem where it would it leave me stranded in the middle of nowheresville west Texas between school and home or work and school or work and home, easily 60 miles between school and home and work and home plus another 30 between work and school. it wasn't until the 70 cougar was long gone that i finally figured out that the tach was the problem, all the rest of the ignition system had been replaced including the dizzy, coil ignition switch, etc, etc.

 

the new 69 cougar will without a doubt be getting the newer 3 wire unit when i have the tach rebuilt. i'll also send the speedo in and have it recalibrated for 140 mph and the tach will be upgraded to an 8K rpm nuit as well.

[PaleRider 12]

Thanks for everyones help. 69Raven that soundls like best plan of action. I know pink wire is still intact under dash I need to trace it to past the firewall to see what was done. Worst case I can run another wire with a resistor on it.

 

Couple of things:

 

1) It was rebuilt using stock 2 wire kit. So i should follow factory type wiring.

 

2) The bypass wire PO did was jumped to fuse box on fuse that heater runs off. Should I splice into wire at ignition or is this sufficient?

 

Again appreciate everyones help.

[bnickel 10,004]

Thanks for everyones help. 69Raven that soundls like best plan of action. I know pink wire is still intact under dash I need to trace it to past the firewall to see what was done. Worst case I can run another wire with a resistor on it.

 

Couple of things:

 

1) It was rebuilt using stock 2 wire kit. So i should follow factory type wiring.

 

2) The bypass wire PO did was jumped to fuse box on fuse that heater runs off. Should I splice into wire at ignition or is this sufficient?

 

Again appreciate everyones help.

 

 

doesn't matter as long as it's ignition hot and dead when ignition off

[PaleRider 12]

Thanks - thats' what I thought - thanks for clarifying. May tie into igntion anyway - seems like a cleaner install. Sounds like I have a plan of attack!!

[bnickel 10,004]

Thanks - thats' what I thought - thanks for clarifying. May tie into igntion anyway - seems like a cleaner install. Sounds like I have a plan of attack!!

 

 

well just make sure you aren't hooking it into the hot wire to the dizzy, otherwise bye-bye freshly restored tach. also it would be better if it was on a fused circuit. i would try to locate a factory wiring diagram and wire it the way it's supposed be if it was me.

[69RavenConv 286]

Bryan's right, any switched 12V is ok to run the Pertronix. As far as killing your tach, you don't need to worry if you use the correct factory harness; the switched 12V will flow thru the tach, thru the resistor wire, to +coil as intended. The splice you need to make is only to tap switched 12V to power the Pertronix. And I agree, doing it at the ign switch makes the most sense.

[PaleRider 12]

Hmm - Just to be clear here is what I was thinking.

 

1. Put in 6 volt coil instead of current 12 (although I'm not sure why this is necessary)

2. Wire tach as it came from factory (i.e., thru pink running to coil)

3. Wire from ignition (on when ignition on - off when it's off) to red wire on petronix inside dizzy. Put an inline fuse to play it safe.

4. Fire it up and stand back ;-)

 

I think this is consistent with I've heard and wiring diagram for Pertronix with balast resistor (attached) - correct?

 

http://www.pertronix.com/support/manuals/pdf/ignitor12vneg.pdf

Edited February 11, 2009 by PaleRider

[69RavenConv 286]

You got it.

 

If you want to use a 12V coil, simply replace the pink resistor wire with a normal 12 ga wire. Everything else stays the same*.

 

(*Actually, it gets easier, because now you can connect the red pertronix directly to +coil instead of at the ign switch, because now they're both 12V)

[PaleRider 12]

Okay tach is now working.

 

Reconnected tach thru harness as it came from factory and ran another wire from igntion directly to red wire on pertronix. Tach seems to be accurate now.

 

Only thing was when I tested factory wiring running to coil it was registering 11.7 volts when igntion was on with or without car running. I expected to be around 9 or so becuase of the resistor. Is this a normal reading?