A buddy on the ORG was having weird problems like that, there's a relay or something in the dash/cluster. He sent it to https://circuitboardmedics.com/ford/
They fixed his problems, don't know if this'll help you or not. You might give em a call.
Here's a quote from their site...
PRODUCT REPAIR DESCRIPTION
This is a Ford Super Duty instrument cluster repair service on 2005, 2006, and 2007 Ford Super Duty (F-250, F-350, F-450, & F-550 SuperDuty) vehicles. The Ford instrument cluster is commonly referred to as the instrument panel, dash cluster, speedo, speedometer, gauge cluster, or cluster. The Super Duty (or SuperDuty) instrument cluster has several common issues including stuck gauges and the battery saver relay circuit. The most common problems are:
Gauges sticking, inoperable, or giving incorrect readings (speedometer, tachometer, coolant temp, fuel, voltage, turbo (Powerstroke) etc.)
Intermittent power to radio, power windows, or interior dome light
Intermittent power to all gauges
Low fuel indicator on at all times with fuel gauge also reading empty
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