[reyn911]

Hello all, thanks for taking the time to help me diagnose this electrical issue I am having. I am new to classic 911 ownership and am looking for advice diagnosing an electrical issue. I have a 1968 Karmann 912 5 gauge car that was converted into a 911 with a 2.2L carbureted engine. I am having a multitude of electrical issues. I have recently replaced the alternator with an updated internal voltage regulator model. I have also removed the existing voltage regulator per the technical bulletin prescribed by Porsche. I am still awaiting parts to finish soldering in the new resistor and plan on replacing the ground strap that goes from the alternator casing to the engine casing.
The battery reads 12.4 volts with everything powered off and then if you turn the key to on everything fires up and lights up as it should (Red alternator light is on). If you then turn the key to engage the starter nothing happens. I tried this two sequential times and then rechecked the voltage on the battery and it read 11.2 Volts. Then about an hour later I went back out to the car with no charger on it and the voltage was again stable at 12.4. I had the battery tested at O’Riellys and it tested good. If I add external power ie a jump starter the car fires up perfectly and runs as it should. However when external power is removed the voltage drops and to 12 volts maximum then the battery slowly drains the red alternator light on the dash illuminates and the car ultimately begins to misfire.

Some other symptoms of the electrical issue are with external power connected and the car running the tachometer/indicators/lights work as they should. When external power is removed the tach works for a period of time unless you add an electrical load ie I turn on the blinker and the tach pins maxed out at 8k RPM while the blinker illuminates and then returns to normal when the light is no longer illuminated. Then eventually as the battery drains the tachometer pins itself at the top of the indication at 8k RPM and other accessories ie the blinker cease to function.

Lastly one stupid question does the red light inhibit the alternator from charging the battery or is just an indication. Sorry I am not an engineer. Thanks again for your time and willingness to help. Hope to see you at a Porsche Parade sometime down the road.