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?

[Howard]

QUOTE (lapuwali @ Dec 12 2005, 10:07 PM)

Your charging system is not working. Does the G light come on with the key (engine off?) YES does it go out with the engine running? YES If it stays out, then check the bulb and then the wiring to it (blue wire from bulb to relay board). The field current for the alternator goes through that bulb, so the alternator will not work if the bulb is burnt out, or the wiring from the bulb to the voltage regulator has come adrift. The other end of the bulb should be connected to the ignition switch (black wire). The next thing to check is the wire from the alternator to the battery (big-assed wire running from the battery terminal on the starter, through the tin, to the alternator). Check the alternator connector at the relay board (three pin connector). Check the relay board itself, to ensure you're getting a continuity between the alternator connector and the voltage regulator connector. ALL APPEAR SOUND If all of that checks out, it's the voltage regulator, or the alternator itself. The VR is mostly tested by swapping it out. The alternator can be tested at many FLAPs.

Thanks, guys. I'm betting battery is good, but how do you do a load test? I want to assume it's the VR, shutting down too soon, but what about that voltage drop?