Ger's 2003 Porsche Boxster S - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Anker · 01-08-2020, 12:32 PM

You must have a bad multimetere. Those voltages are too high!

geraintthomas · 01-08-2020, 12:46 PM

Quote:

Originally Posted by Anker

You must have a bad multimetere. Those voltages are too high!

Interesting! I'll check with another. You set it to 20v right?

Nine8Six · 01-08-2020, 01:02 PM

Quote:

Originally Posted by geraintthomas

Interesting! I'll check with another. You set it to 20v right?

DMM set of 20V(dc) is correct.

The +2V difference from car OFF to ON is sufficient to confirm your alternator is still in good shape and charging.

I'm guessing your DMM just needs to be re-calibrated. If you pop open the enclosure you should find 1 (or more) resistor/potentiometer. One of those should be for voltage offsetting (you'll need a known voltage source to calibrate it). Plenty of tut online/YT.