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?

[ClayPerrine]

The volt meter in the center console is nowhere near accurate. You can use it to see if your brake lights are working (voltage drop when you step on the brakes) and it will twitch with the turn signals, but it being an accurate measurement of voltage, well forget it.

The gauge is connected to the same power source as all the other instruments. So it has lots of connections and other stuff in the circuit to affect its performance. If you want it to be more accurate, run two heavy wires, one red, and one brown all the way back to the battery. Use a relay to switch the brown one off when the car is not running. After doing that, it still may not read correctly, as the calibration is questionable.

Or just ignore the gauge. (IMG:style_emoticons/default/biggrin.gif)