I've had similar problem with charging volts fluctuating,sometimes normal-then lower. One thing you can check is the auxillary positive battery post by the fusebox when the car has been running for a bit and charging volts appear lower. Take the red cover off and feel if is warm or hot. If it is,then a good cleaning is required by unscrewing that nut and wire brushing all wires under there. Disconnect ground first and don't overtighten when replacing the aux. pos. post. nut as it seems zinc threaded. I have done this a few times and the volts output went back to normal. Hopefully I am hitting the nail right on the head! good luck Rayday