I had one car overcharge like that. The wiring harness that runs along the front of the engine had a broken wire where it was zip tied from factory. Might be worth a look. The one I found was in the harness near where it curves and runs along the top of the transmission(the zip tie closest to the drivers side of the engine). If that makes any sense? It was overcharging and making the battery light come on, after wire was repaired it went out and charged normally (14.3v ish)
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View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 37.7 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.3 mpg (Imp)