Is it normal for all of the gauges to fan full right, then full left, then read normal? Additionally, I filled up with gas the yesterday and the gauge failed to move to full from a quarter tank. When I shut the car off and restarted it, the fuel gauge kind of ground to the full level. Since then, the gauge has responded normally with the exception of the fanning right and left.

A friend of mine has a full size Ford truck. His did the gauge fanning and shifted funny. He replaced the battery and everything went back to normal including shifting smoothly.

Additionally, the light sensor flashes the headlights on and off in the morning (dealer couldn't replicate the problem even with a cell phone video). I also had a new alternator put on and in the morning under full load (seat heater, rear defrost, radio, headlights, driving lights, fan blower) it drops the gauge from 15 volts to around 9 and the lights dim. When the rpms increase, the charge needle jumps to 15 volts. When the car warms up, it charges normally even under full load.

Are these symptoms of a battery issue? Original battery in an 04 GXP with 80k.

The gauge'* fanning is normal. As for the other stuff, I'm not sure. Hopefully a GXP person will be in pronto for more info.

yah I would say your battery is going out, thats what mine did when it went out, 6 years has worn her out, I like Duralast Gold as a replacement, just make sure you get the one with the special vents that hook into the vent tubes in the car

...and even if it'* not the battery, it'* relatively cheap to replace. That old battery owes you nothing.

Fanning is a normal programmed function of the GXP. Also, if you start the car right after shutting it off, the engine will fire immediately but the gauges take a few seconds to "wake up". If the car starts ok in the cold, I wouldn't replace the battery.