Chapter 8. Failure Diagnosis; Outline Of Control; When The Defrosting Failure Is Doubtful; Re-Setting Of Microcomputer At Power Failure - Sharp SJ-F750SP-BK Service Manual

CHAPTER 8.
SJF800SPSL
FAILURE DIAGNOSIS

[1] OUTLINE OF CONTROL

1. ON/OFF Control of Compressor
• ON/OFF of the compressor will be controlled depend on the temperature detected by
the R-thermistor and F-thermistor. (Normal cooling control)
• In case the surrounding temperature is high at the power supply input, the compressor will be ON at once and the normal cooling control will start
after several hours.
• When the rapid ice making or rapid freezing is requested by user during the operation, the compressor will be ON and cooling operation will be
started regardless of the detected temperature by the thermistors. However, if requested during the defrosting operation, the request will be exe-
cuted after the completion of defrosting and ON of the compressor might be delayed.
• During 5 minutes after the compressor stops, it will not start regardless of the detected temperature by R-thermistor and F-thermistor.
2. Defrosting
Microcomputer calculates the appropriate timing of defrosting and defrosting is made automatically. Therefore no manual operation by user is
required. The cycle of defrosting varies depend on the usage condition of the refrigerator. (Maximum time about 50 hours, minimum time 8 hours)
3. Thermistor
Thermistors are installed in 4 places; in the refrigerator and freezer compartment, and close to the Control panel and Evaporator. (R-thermistor, F-
thermistor, Outside temp-thermistor, Def-thermistor)
R-thermistor and F-thermistor detects the temperature in the refrigerator and freezer compartment respectively and controls ON/OFF of compressor.
Def-thermistor detects the temperature around the evaporator and shows the progress of defrosting.
Outside temp-thermistor detects the surrounding temperature of refrigerator. It decides the defrost timing and changes the operation mode when the
outside temperature is high.

[2] WHEN THE DEFROSTING FAILURE IS DOUBTFUL

Execute the Self-Diagnosis Mode. (Refer to the Chapter "SELF-DIAGNOSIS MODE")
• In case the diagnosis result is "EE03" (Def-thermistor system defect), follow up the flowchart of EE03. (In case of any abnormity in the Def-ther-
mistor, defrosting will not be made for safety reasons.)
• In case the diagnosis result is "EE07" (Defrost defect), follow up the flowchart of EE07.
(This diagnosis result will be displayed when defrosting is made for 120 minutes, the maximum time length. In this case, the defect of PWB itself
and also the breakage of heater and heater circuit (melt down of current fuse and temperature fuse) are considerable.)

[3] RE-SETTING OF MICROCOMPUTER AT POWER FAILURE

• At the power failure for over 0.4 second, the control of the microcomputer will might be reset.
• Microcomputer might continue to operate for approximately 10 seconds maximum at power failure depending on the load at the operation. Approx-
imately 30 seconds is necessary for the definite power OFF condition.
• When the power is re-supplied, the normal cooling will be resumed.(If cold enough in the cabinet, the microcomputer will begin defrosting in 40
minutes according to the condition.)
• The temperature and operation mode set by user will be maintained even if a power failure occurred.
(However defrosting, rapid freezing, rapid ice making, and timer will not be maintained.)
• When the self diagnosis is made, each mode and setting are resumed to the initial condition.
Service Manual
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SJF800SPSL