[dsmghost]

From prosport, it's usually a bad sending unit (if electric). It should have a sticker showing a range of resistance, ohm the sender with a dvom. I have bought 2 gauges from prosport both senders tested bad brand new, I'm still waitng for a resolution from prosport 6-7 months later. Buy a nicer gauge like autometer. And to be sure check, with a different mechanical gauge.