Electrical help Options

[Howard]

A rare serious question from me. 73 914 2.0 FI. Pretty stock. Battery runs down, especially when lights are being used. Battery is good (Optima) and charges up to 13.7 volts. Reads that on my tester, which agrees with the in car ammeter. After starting, is slowly drops to just under 12v. Using the brake lights, turn signals, parking lights, back up light drops to 10v.
Wipers, emergency flasher, cig lighter cause no drop in reading. After turning off the lights, it only recovers to 12v, not the almost 14 I started with. Run with the lights on for 2 hours or so and car won't start. Quick charge or jump and I'm on my way, but battery will only recover after home recharging. WTF?

[lapuwali]

If you add load, the extra power has to come from somewhere. The VR allows the alternator to provide more or less current, depending on the load (and this load is drawn from the engine itself). If the alternator isn't working, then the battery is presented with these varying loads, but it can't provide the extra power. It's normal during starting for the voltage to drop to 9-10v simply because of the huge load the starter puts on the battery.

If you start with a fully-charged battery, turn on the key (engine off), and hit your brake lights, or turn on your headlights, you'll see the voltage drop as you add load.

My money is on your alternator and/or VR having crapped out. But, check the wiring first, and you may save yourself the supreme hassle of pulling the alternator, or buying a VR only to find it doesn't change anything.