Hi Rich, If the gas gauge is new (even 10 years old) it is very possible the needle is getting stuck on the glass of your gauge cluster. The replacement gauges are well-known to have this problem. The Chinese folks mis-measured them or something. You may even be able to see this happening if you look closely. Honestly your gas gauge will work on 12 volts (mine has been doing so for 40+ years with no reducer). If you decide the needle rubbing on the glass is the problem, one way to fix it is to loosen all 4 nuts holding the cluster to the dash, push it back enough to carefully remove the trim ring and glass panel, carefully remove the rubber ring in the cluster (the one that keeps the glass from rattling) and put something behind it that's about 1 to 1.5mm thick. Could be a ring cut out of a cereal box, a piece of inner tube cut in a ring, whatever. You just want to keep the glass from going in as far as it is right now.
Your fuel gauge isn't fried and that voltage reducer may not even be needed. Please let us know if you can see what the needle is doing.
