Adaptive Defrost Theory Of Operation - Amana SXD25S2 Service

Electronic Functional Description
WARNING
To avoid electrical shock which can cause severe personal injury or death, disconnect power to
refrigerator using power switch before servicing. Wires removed during disassembly must be replaced on
proper terminals to insure correct grounding and polarization. After servicing, reconnect power using
power switch.
Adaptive Defrost
After designated compressor run time, refrigeration
cycle is interrupted and electronic control sends a low
voltage signal to defrost relay coil (def D1).
Powering the relay coil closed relay contact (D1)
completing high voltage circuit to defrost heater
through closed defrost terminator (closes at 15°F).
Isolator, which is part of high voltage PC board,
recognizes presence of line voltage to defrost heater
and sends low voltage signal to electronic control.
Electronic control keeps count of number of minutes
defrost terminator remains closed (opens at 48°F).
RS1300003 Rev. 0
IMPORTANT: When the power switch is OFF , the
isolator see's line voltage which keeps the
electronic controller from signaling the
evaporator fan motor or the compressor relay
coils and also keeps the damper heater off.
Length of time defrost terminator is closed determines
if the next defrost cycle advances by 4 hours of
compressor run, stays at the same interval, or delays
by 4 hours of compressor run.
If defrost terminator does not open before 29 minutes,
defrost cycle is automatically terminated by electronic
control and refrigeration cycles will resume after 6
minute dwell time.
36 December 1997