Hello opposite direction fuel gauge. The fuel gauge runs opposite when tank is full it registers empty and when tank is empty gauge registers full. Help

 

Is the car new to you? Was there recent work done to it? Did it just happen...one day it worked correctly and now it's bass ackwards? The fuel level sender is resistance based...you can check proper operation with an ohm meter and the specs from a manual but if it's operating exactly backward I'd be inclined to think either the sender is wired backwards or possibly the gauge is bad. Need to check your ohms for sure...