Ford E150 2002 Owner's Manual page 15

Never remove the coolant reservoir cap while the engine is
running or hot. Steam and scalding liquid from a hot cooling
system can burn you badly.
This gauge indicates the temperature of the engine coolant, not the
coolant level. If the coolant is not at its proper level the gauge indication
will not be accurate. If the gauge enters the red section, the oil
pressure/engine coolant and Check Engine/Service Engine Soon
indicators illuminate, refer to What you should know about fail-safe
cooling in the Maintenance and specifications chapter.
Engine oil pressure gauge
Indicates engine oil pressure. At
normal operating temperature, the
needle will be in the normal range
(the area between the "L" and "H");
if the needle goes below the normal
range, stop the vehicle as soon as
safely possible and switch off the
engine immediately. Check the oil
level. Add oil if needed (refer to Engine oil in the Maintenance and
specifications chapter). If the oil level is correct, have your vehicle
checked at your dealership or by a qualified technician.
Battery voltage gauge
Indicates battery voltage. If the
pointer moves and stays outside the
normal operating range, have the
vehicle's electrical system checked
as soon as possible.
Instrument Cluster
18
8
15