FORD 2003 F-550 v.2 - Manual (Page 19)

Red area (over temperature) —
the transmission fluid is overheating.
Stop the vehicle to allow the
temperature to return to normal
range.
If the gauge is operating in the Yellow or Red area, stop the vehicle and
verify the airflow is not restricted such as snow or debris blocking airflow
through the grill. If the gauge continues to show high temperatures, see
your Ford dealer.
Instrument Cluster
19