Have you double checked your wiring? And is the gauge a new one or one you re used? The gauge maybe bad or the alt may not be charging that battery. I always find that it is the simple things that mess me up. My turn signals were not working. I checked the fuse panel and when I pulled the signal fuse it tested good. Come to find out, I had installed the fuse block upside down. And i was reading the cover wrong. When i turned the cover upside down and found the signal fuse it was blown. So check the simple thing first and go down the line. You may have one of your wires in the wrong place.
