Is the compass working corrrectly?
If so, it could be the ambient air temperature sensor.
I had a similar issue, and this was the fix. The sensor is located on the radiator support, just in front of the radiator. Ford used a couple different ones, one black and one brown. The wiring connectors were clocked differently and it took two trips to the parts store to get the right one as I didn't bring the original with me.
Save some time, pull the original and get a replacement. Less than $30 if I recall correctly...