Fujitsu ASU18RMLQ Service Instruction page 23

Defrost Flow Chart
The defrosting shall proceed by the integrating operation time and outdoor heat exchanger temperature as follows.
Outdoor heat exchanger temperature: Over 53.6°F (12°C)
Compressor ON time: Over 15 minutes
Heating operation start : Compressor ON
Compressor integrating
operation:
45 minutes and over
Outdoor temp. > 30.2°F Outdoor temp. < 30.2°F
=
(-1°C)
Outdoor heat exchanger Outdoor heat exchanger
temperature: temperature:
Below 17.6°F (-8°C) Below 14°F (-10°C)
Defrost start
Defrost Indicator:
[Operation lamp]
7 sec ON / 1 sec OFF
or
Defrost end
01-20
(Not defrosted for 6 or 10 minutes)
(-1°C)
Outdoor fan motor OFF
4-way valve OFF
Compressor ON
(Frequency : 92 Hz)