Step 6. Set Fan Operation Switch - Honeywell CT3600 Owner's Manual

When the batteries are running low, a REPL BAT message flashes for one to
two months before the batteries run out completely. Replace the batteries as
soon as possible once the message flashes.
IMPORTANT
Although the thermostat has a low battery indicator, replace the
batteries once per year to prevent leakage and to prevent the ther-
mostat and heating/cooling system from shutting down due to lack
of battery power in the thermostat.
If you insert new batteries within 20 to 30 seconds of removing the old
batteries, the system retains the current time and day. If the display is blank,
the batteries are dead or installed incorrectly. You must reset the time and
day. Refer to Set the Clock for instructions.
As a precaution when leaving home for longer than a month, change batteries before leaving to prevent
the system from shutting down due to lack of power. Always use fresh alkaline batteries. Nonalkaline
batteries do not last as long. They also can leak, causing damage to the thermostat and the wall surface.

STEP 6. SET FAN OPERATION SWITCH

The thermostat fan operation switch, labeled FUEL SWITCH is factory
set in the F position. This is the correct setting for most systems. If your
system is an electric heat system, set the switch to E. The E setting
allows the fan to turn on immediately with the heating and cooling in a
system where the G terminal is connected.
69-1642 10
M16424
FUEL SWITCH M12676