Residual Power at Auxiliary Power/Cigarette Lighter Socket with Ignition OFF

[StealthyBlagga]

My 2012 Tiguan has some residual power reaching the Auxiliary Sockets even with the ignition switched off. Not enough power to charge a phone, but enough to light up the charger's LED. When the ignition is switched to the "accessory" or "on" position, I get full power (enough to start charging my phone).

DC voltage measured at the socket with ignition OFF is ~10-11V (and drifty). DC voltage measured at the same socket with ignition ON is ~15V. All the auxiliary sockets in the vehicle are behaving the same. The fuse looks fine (I didn't really expect otherwise, but ran out of things to check).

This residual voltage is causing me some trouble with a dashcam, so I'd like to get to the bottom of it. Any ideas? Is there maybe a solid state relay somewhere in the ignition circuit that could be leaking? Faulty ignition switch? Other?

[Adders]

My 2011 TDI Tiguan is the same and I have always thought it is a characteristic of the VW computer based electrical system. On my car when the ignition switch is switched off the voltage at the auxiliary sockets eventually decays to almost zero. I have measured 0.9 volt at the auxiliary sockets even after the ignition has been switched off for 20 hours.

I have a 2 way radio, GPS and phone car kit wired directly off the battery via a relay that is switched by the auxiliary socket circuit. This means these accessories always get the correct voltage, however when the ignition is switched off it takes approx 15 minutes for the voltage in the auxiliary socket circuit to decay sufficiently for the relay to disconnect. In my view this is not a bad thing as I can make a short stop such as for fuel without the GPS etc not switching off.