Yes and Yes.
First of all. Did you ACTUALLY follow directions? Do you have a 12V source supplied to power the unit? Did you buy their coil? Pertronix unit failures that everyone likes to blame on Pertronix is 99% of the time on the head of the installer.
Yes, I have a factory tach car too. No, the Pertronix II will NOT work without some re-wiring. The III not at all. Anyone that tells you they do should offer to replace your tach.
It will ruin the tach if you don't make the changes, not to mention the tach won't read correctly or at all.
Because of what my car is I hid the installation to all but the most observant.
I will give you basic instructions. I will even offer my phone number to you in PM if you need verbal instruction. I've done four cars personally and have helped many Shelby guys with this instruction.
You'll need to pull your instrument bezel. Locate the red tach wire. It's plugged into the tach with a bullet connector to the right side of the car . This step you have two choices.
You can make a Y connecter with the factory style bullet connectors or the K.I.S.S. method and simply use a scotch Lok. The latter is the quickest way.
You'll need about six feet of Red 16 Ga wire. ( I used black to hide it with the engine harness.)
Use a Fish tape or a coat hanger with a small tightly bent loop and feed it through the rubber grommet where the ignition harness comes through the firewall. You can use a bit of dish soap to assist with the insertion and pulling the wire through. It takes a little bit of effort to get the hanger/Fish tape worked through next to the wires in the grommet. Be gentle! Once the hanger/ Fish tape is through push it forward far enough to get your hands on it in the opening of the instrument cluster you removed. Strip about 2-3" of the end and put it through the small loop you bent into the end of the hanger.
Twist the bare wire back on itself and wrap the loop/wire with a piece of electrical tape. ( Just to keep the loop edge from catching the grommet/wires when you pull the red wire in from the firewall side of the grommet. Clip the wire from the hanger once your on the the firewall side of the engine compartment pull enough wire to go about 12" past the coil. Now return to the car are cut the wire long enough to protrude past the dash opening about 8". If you're going to use the Scotch Lok, Scotch Lok the wire you pulled with the Red Tach lead. Do so BEFORE the bullet connector on the body-side of the harness. You'll then want to return to the engine compartment and run you new wire with the factory oil pressure/water temp/coil feed harness.
You'll attach the new red wire to the red wire on the Pertronix ignitor. You can solder and shrink tube, use a crimp on bullet connector or butt splice the wires. I prefer the bullet connector so the distributor can be removed from the car instead of setting it to the side or unplugging the engine harness at the firewall.
You coil will be wired as it was from Ford. Red wire with factory plug to the + side of the coil. The black wire with eyelet goes to the - side of the coil.
Once you've completed the engine side you can test the unit before putting the instrument cluster back in.
Plug the two wires that the tach is plugged into together. The car will start and run.
Once you've confirmed this assemble the car. The tach will read correctly and the Pertronix will have 12V constant as it requires.
