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I measured my "cigar socket / outlet" with a multimeter. Instead of 12v it had 19v. Is this normal? Is it my voltage regulator, alternator, battery that has problems?

Car: Peugeot 307, 2.0 XSI 2003 The 12v "cigar socket / outlet" is off when my key is turned off, and on when I turn it on.

Additional information: Battery is almost 1 month old. Mechanic replaced it.

Voltage car off with key not inserted
Battery -  12v socket
16,67v     0v

Voltage car off with key turned 2/3 steps
Battery -      12v socket
not tested     18,2v

Voltage car on
Battery -  12v socket
20v        20v

Voltage car, airco, headlights on
Battery  - 12v socket
20v        20v
  • 1
    Did you check the voltage output at the alternator as well? – Pᴀᴜʟsᴛᴇʀ2 Mar 28 '15 at 11:31
  • I guess I should have first asked if the car was running or not (with key not just in the acc position) when tested? – Pᴀᴜʟsᴛᴇʀ2 Mar 28 '15 at 13:04
  • I've added additional information in my question above. Thanks – MOTIVECODEX Mar 28 '15 at 14:36
  • 2
    Are you sure your voltmeter is working properly? – Paul Mar 29 '15 at 18:58
  • @Paul I am going to the mechanic tomorrow. I think and hope my multimeter is busted. Tested it with my power supply and it gave +2 volts readings. Still the car battery would be too high, even with +2 volts wrongly added volts.. – MOTIVECODEX Mar 29 '15 at 20:29
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Went to the mechanic, and the voltage looked good at 14,4v +- when everything (car, airco, lights, radio) were on. Looks like my multimeter is busted. Need to buy a new 9v battery for my multimeter to test if that fixes the offset, or I'll try to calibrate my multimeter.

Anyways, always test with another multimeter if in doubt.

  • 1
    You can also test on a known source, which is a procedural requirement for professional electricians. – Paul Mar 31 '15 at 21:45
  • Yes, I did that and it gave wrong values. Even with a new battery + some calibration it still has big differences. Time for some a new multimeter. – MOTIVECODEX Apr 1 '15 at 18:00

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