If unit operates

 If unit operates properly on the heating cycle, raise the
heating temperature setting high enough until the heating
second-stage mercury bulb (lower) makes contact.
13. Supplementary resistance heat, if installed, should now
come on. Make sure it is operating correctly. If outdoor
thermostats are installed, the outdoor ambient must be
below the set point of these thermostats for heaters to
operate. It may be necessary to jumper these thermostats
to check heater operation if outdoor ambient is mild.
14. For thermostats with emergency heat switch, return to
startup (Step #9). The emergency heat switch is located
at the bottom of the thermostat. Move this switch to
emergency heat. The heat pump will stop, the indoor
blower will continue to run, all heaters will come on and
the thermostat emergency heat light will come on.
15. If checking the unit on the heating cycle in the wintertime,
when the outdoor coil is cold enough to actuate the defrost
control, observe at least one defrost cycle to make sure
the unit defrosts properly.