Mine sits in garage was cold but nit as cold as its been, I’ve seen my gauge at 13,14,15 .....normal. today for about 30 min it was high but was low again by the time I parked it, an hour and a half later. I have dual batteries in parallel and this is completely normal function of this charging system. On the neg cable off the battery there is a sensor to monitor voltage from battery, when its voltage is lower alternator charges when normal voltage alternator stops alternating (lol-joke) if you want, remove that sensor and youll get a more (i dont want to say accurate but...) normal-ish reading. It does no harm disconnecting this sensor.View attachment 190293
Is this the part? Or do I have to replace the entire negative battery cable?