Haier Refrigerator: Judgment of Soft Failures in Temperature Controllers
Technical release by the Beijing Haier Refrigerator After-sales Service Center on September 23, 2011.
A soft failure in a temperature controller refers to a situation where the temperature controller itself has no fault, but rather the defrosting mechanism control values are either too high or too low:
(1) The control value range for temperature is either too high or too low; the temperature difference range is either too large or too small; it does not meet the requirements of the refrigerator, meaning the internal temperature of the refrigerator is either too high or too low; the compressor starts too early or fails to start in winter; the compressor turns on and off too frequently or remains on/off for too long. The sensing tube of the temperature controller is inserted into a constant-temperature bath containing alcohol, with the alcohol's temperature adjustable from +10°C to -24°C via the constant-temperature bath. A thermometer is inserted into the alcohol to observe its temperature. The two terminals of the temperature controller are connected in series with a battery and an indicator light. When the switch of the temperature controller closes, the indicator light turns on; when the switch opens, the indicator light goes out. Changing the temperature of the constant-temperature box can make the temperature controller close or open. During testing, first adjust the temperature controller to the hot spot position. Under normal temperature conditions, the switch of the temperature controller closes, and the indicator light turns on. Lower the temperature of the constant-temperature box and observe the indicator light. When the indicator light goes out, record the temperature of the constant-temperature box. This temperature represents the actual disconnection temperature of the temperature controller at the hot spot. If this temperature differs significantly from the standard temperature value, then the temperature controller has a soft failure. It is also possible to observe the on-off temperatures at the midpoint and cold point of the temperature controller to determine if there is a soft failure.
(2) Maintenance of Soft Failures in Temperature Controllers
① For fixed-temperature reset type temperature controllers. If the cut-off control temperature of the temperature controller is too high, it indicates that the internal temperature of the refrigerator does not reach the predetermined requirement before the compressor stops running. In this case, rotate the temperature range adjustment screw clockwise by 1-2 turns. If the cut-off control temperature is too low, the compressor runs for too long, and the internal temperature of the refrigerator is too low. Rotate the temperature range adjustment screw counterclockwise by 1-2 turns. If the defrosting temperature of the temperature controller is too high, the internal temperature of the refrigerator rises, yet the compressor still does not start. Rotate the defrosting temperature adjustment screw counterclockwise by 1-2 turns; conversely, rotate the defrosting temperature adjustment screw clockwise. If the temperature difference between the on and off states of the temperature controller is too small, the compressor will turn on and off too frequently. Rotate the temperature difference adjustment screw counterclockwise; conversely, rotate the temperature difference adjustment screw clockwise.
② For semi-automatic defrost temperature controllers, rotating the temperature range adjustment screw clockwise will simultaneously increase the on and off temperatures of the compressor. Rotating it counterclockwise will simultaneously decrease the on and off test temperatures of the compressor. Rotating the defrost adjustment screw clockwise increases the temperature, while rotating it counterclockwise decreases the temperature, without affecting the on and off temperatures. Rotating the temperature difference adjustment screw of the temperature controller clockwise narrows the temperature difference, and rotating it counterclockwise widens the temperature difference. Its adjustment affects changes in the on temperature but does not affect the off temperature.