Service Manual

21
7) Defrost–The defrost icon turns on and "dEF" is displayed during defrost. There is a
5-min. minimum defrost time and a 1-hr.maximum defrost time, and a 5-hr. defrost
interval.
1a) Time-Initiated: 5-hr. cumulative Comp run or 4-hr. continuous Comp run defrost
timer terminates (Comp energized more than 5hrs.). Defrost icon turns on and
"dEF" is displayed. DHenergizes. Comp and EvapFM icons turn off. Comp, ConFM,
and EvapFM de-energize.
1b) Manually-Initiated: To initiate a manual defrost, press the manual defrost button on
the display. Defrost icon turns on and "dEF" is displayed. DH energizes. If on, Comp
and EvapFM icons turn off. Comp, ConFM, and EvapFM de-energize.
2) Defrost-Termination:
(1) DTh warms to 77°F (25°C). If not, conrm DTh status. See "II.D. Thermistor
Check." If DTh is in proper range. DH de-energizes. 3 min. Comp delay timer
starts. Defrost icon and "dEF" continues.
(2) 3 min. Comp delay timer terminates. Comp icon turns on. Comp and ConFM
energize. 4-min. EvapFM delay timer starts. Defrost icon and "dEF" continue.
(3) 4-min. EvapFM delay timer terminates or the defrost thermistor cools to 15°F
(-9°C), EvapFM icon turns on and EvapFM energizes. 15-min. temperature
display delay timer starts. Defrost icon turns off, "dEF" continues. Note that
the 4-min. EvapFM delay time is a maximum; if the defrost thermistor cools to
15°F(-9°C) before the 4-min. EvapFM delay timer terminates, EvapFM icon
turns on and EvapFM energizes. Also, when the cabinet temperature is above
50°F (10°C), EvapFM delays energizing until the cabinet temperature is below
50°F (10°C).
(4) 15-min. temperature display delay timer terminates. Cabinet temperature
replaces "dEF" on CM display.
Note: Pressing the defrost button on the display terminates defrost. If the cabinet
temperature is above setpoint, Comp icon and EvapFM icon turns on and Comp,
CondFM, and EvapFM energize.
Defrost Diagnosis:
1) Time-Initiation or Manual Initiation: Time-Initiation; 5-hr. Comp cumulative run or
4-hr. continuous run defrost timer terminates. Manual Initiation: CM defrost button
pressed.
Note: There is 5-min. minimum defrost time and a 1-hr. maximum defrost time.
(1) CM, Comp, CondFM, and EvapFM Diagnosis: Conrm defrost icon turns on,
"dEF" is displayed, and Comp and EvapFM icons turn off. If not, replaceCM.
Next, check that CM 1 (C) (V) and CM 5 (F) (DBU) do not have 115VAC to
neutral (W). If 115VAC is present, replaceCM.
(2) DH Diagnosis: Conrm DH energizes (amp draw). If not, check for 115VAC at
CM 4 (H) (R) to neutral (W). If 115VAC is not present and defrost icon is on,
replace CM. Next, check for 115VAC at DT (BK) to neutral (W). If 115VAC is not
present on both DT black (BK) wires, check DT continuity. If open, let cool and
reset. If DT does not close, replace DT. If DT is closed, check DH amp draw and
continuity.