Several years ago, I converted the truck from its original 1G (first generation) alternator to a 3G alternator. It’s a 130 amp unit, which was better than the old 65 amp unit. Here’s the forum thread I read prior to doing my conversion. It’s pretty straightforward, if not easy.
Anyway, the conversion left me without a working amp gauge, because the wiring that FoMoCo uses as a shunt no longer is connected to the (eliminated) voltage regulator. RCCI to the rescue!
For the small sum of $55 (shipped), RCCI sells a replacement amp gauge that is converted to a volt gauge, using a new movement. The gauge face is perfect, and the needle comes repainted the bright orange that the factory used. It’s beautiful except that the rest of the dash is old and faded. I’ll learn to live with it. The new gauge is a sight to behold:
The old dash is pretty faded, so the new gauge really stands out:
Rocketman does an outstanding job with these conversions, and I wish I’d done this a LONG time ago.
When the truck is off, the needle is at “D” (0 volts): when the ignition is on, but the engine is off, the needle is just under the halfway mark. (actual battery voltage) When the engine is running, the needle is somewhere between just over half scale and past “D” (actual charging voltage). It’s something I’ll have to get used to, but I’m confident that it’ll give me a good idea about the condition of the charging system.
You can find the wiring diagram to this conversion HERE.
I used a relay to turn the angry pixies on and off at the alternator cable (connected to the mega fuse) to control the voltage going into the gauge;this allowed me to use the stock amp gauge wires, and simultaneously get voltage within 18″ of the alternator output.
If you’ve got an old Ford/Mercury that the ammeter doesn’t work, please consider installing one of these gauges.