Voltage reading differential between multifunction display and external volt meter. |  |  |
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Laz - 2 months ago |
The following is one example of several. The numbers change, but their approximate relationship remains the same.
I've had my 13 Boxster S, sitting overnight, locked, with no maintainer attached, but with a voltmeter connected by power plug to the footwell outlet.
The reading is 0 as expected, then when the car is unlocked and "wakes up" the reading goes to a healthy 12.67.
When the key is turned in the ignition so as to read the multifunction voltage display, the external voltmeter reading understandably starts to drift down, but in simultaneously observing the car display, (a good peripheral vision exercise) it's always about .6 to .8 of a volt lower. I would think the multi display takes readings from very close to the battery and/or alternator, and that the power outlet, if anything, would show a lesser reading, being ostensibly farther from the voltage source. So,
a) Can anyone here explain this?
b) Assuming the multi display is inaccurate, is there a system calibration/adjustment that can be done, say via PIWIS?
Edited 3 time(s). Last edit at 09/12/2025 01:11PM by Laz. (view changes)
I've had my 13 Boxster S, sitting overnight, locked, with no maintainer attached, but with a voltmeter connected by power plug to the footwell outlet.
The reading is 0 as expected, then when the car is unlocked and "wakes up" the reading goes to a healthy 12.67.
When the key is turned in the ignition so as to read the multifunction voltage display, the external voltmeter reading understandably starts to drift down, but in simultaneously observing the car display, (a good peripheral vision exercise) it's always about .6 to .8 of a volt lower. I would think the multi display takes readings from very close to the battery and/or alternator, and that the power outlet, if anything, would show a lesser reading, being ostensibly farther from the voltage source. So,
a) Can anyone here explain this?
b) Assuming the multi display is inaccurate, is there a system calibration/adjustment that can be done, say via PIWIS?
Edited 3 time(s). Last edit at 09/12/2025 01:11PM by Laz. (view changes)
I infer from your response there likely isn't a direct issue with the battery itself, nor the functionality of the voltage supply.
Not that I'm losing sleep over it, but I wonder if a calibration could be done to compensate.
Once the car is started the voltages seem to be more in line as (I think) the readings are produced by the alternator.
Not that I'm losing sleep over it, but I wonder if a calibration could be done to compensate.
Once the car is started the voltages seem to be more in line as (I think) the readings are produced by the alternator.
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