Did ya try putting some fuel in it?
Does the light still work properly or is it on all the time? If the former, check the connector under the tank. Sounds to me like a bad gauge or buggered connector. IIRC the dash light and the guage read the same signal wire (y/wh) so if the light is still working properly then the float is probably still good. If the latter, then the float is most likely the culprit. But I'm no diagnostic expert, maybe others will chime in to confirm.
'05 'Train FXSTBI -
decked heads .036, ported, Crane 310-2 cams, 150 fat front, exile pipes, lowered 2", coil relocation, Todds Cycle 10" chubbys, foot clutch/jockey shift, pro 1 0* trees, Grip Ace, Exile internal throttle, homemade rocker box speedo relo, blackline dash, and lots of black!.HP = 81.94 TQ = 93.72.