Voltage discrepancy, WTF? Options

[saigon71]

As long as I can remember, when driving at night in the 914, my center console voltmeter hovers right around 12V when cruising with the lights on. When I hit the brakes, it drops well below 12V...anything else drops it even lower.

I'm running an Optima Red Top near the end of it's service life and want to make sure my charging system is healthy before popping on a new AGM battery.

I had been considering switching to LED headlights and brake lights to lower the current draw.

I hooked up the VOM at the battery and did a load test with the car running, adding an accessory at a time.

With headlights, brake lights and aux fan on the voltmeter in the center console read just over as 10 volts, while the VOM hooked to the battery showed 12.58V. Is this discrepancy normal?

[Spoke]

With headlights, brake lights and aux fan on the voltmeter in the center console read just over as 10 volts, while the VOM hooked to the battery showed 12.58V. Is this discrepancy normal?

As others have noted the difference is expected in the 914 because of small gauge wire causing IxR voltage drops as loads like headlights, turnsignals are active.

I've measured my gauge separately and found the gauge to be accurate to about 0.1V. Unfortunately where it resides in the 914 wire loom causes the gauge to read very low at times.

Although not an accurate measurement of battery voltage, the gauge does give an indication of the voltage going to loads in the 914. For instance the headlights may only be getting 10V instead of 14V which the alternator puts out at elevated RPM.