05 gas gauge 5.4L short bed
 

Fuel gauge moves up to E and drops back down on start. Checked sending unit ohms from 15 empty to 150 full. Pulled instrument cluster and checked ohms at connecter pins 8 - 10. 78ohms with about 3/4 tank. Drove 80 miles checked it again 46 ohms. Got another cluster - installed it - doing the same thing. What else can I try?

Can anybody tell me where the power to the fuel gauge is? A schematic of harness to see which wire is supposed to power gauge?