any reason why my gas gauge would stop working. after switching over to 12 volt. i then replaced the gas tank with a new one. the sending unit is the old one. i have the 12 to 6 volt reducer on the gauge. it was working the other day. after replacing the tank I put some gas back in it and it was reading almost empty cause i only had in about 4 gals. now it is reading full when it doesn't have much in it. turn the key off and it goes down to empty. key on and it reads full.