DIY Network

Bonneville with 105K. 3800 motor. The charging gauge on the dash is sometimes below 12 or 13 volts. Replaced the alternator, belt and swapped the battery with another car. Removed all the battery cables and cleaned them. Removed the ground from the chassis and cleaned it. The gauge will still float from 14 down to 12. I question the way it operates because for many years the gauge stayed at 14 volts while the car is running. I think I can hear the blower motor change when the volts drop down. I have not been able to identify any cause for the fluctuation when shutting different things on and off. The only thing that does not work properly is that the A/C does not blow as cold of air as it used to.
Thanks in advance. Mark

You verified this with a volt guage on the battery? Or just the posible defective one on the dash?