Richard,
With erratic idling it sounds like a potential throttle body/pedal potentiometer issue.
Might be best to get the error codes causing the EOBD light checked out.
At some point soon it may well go into ‘limp home’ mode.
As an aside, I took my 3200 out on Sunday. Voltmeter dial varied between 12-14 volts depending on the mood the car was in (nothing to do with the load on the car)! My first 3200 was exactly the same.