Other causes can be:
If your dehumidifier wonít start the problem may be with the float assembly. This device is located near the bucket and is used to activate the auto shut off or bucket level switch. This is a safety device to prevent the unit from overflowing. When the switch is tripped, power to the compressor and fan motor circuits is disrupted until the bucket is emptied or properly positioned. If your dehumidifier wonít start, check the operation of the float to ensure that it moves freely and contacts the level switch properly.
If your dehumidifier wonít start the problem may be with the humidity control or humidistat. This component monitors the relative humidity in the air and then supplies power to the compressor circuit through a set of internal electrical contacts when the level exceeds the userís set point. If the electrical contacts in the control have failed or if the ability to detect the correct relative humidity is not within tolerance, then the control will need to be changed. Rotate the dial and listen for a distinct click sound or monitor the contacts with a multi-meter to determine if the control is defective.
If your dehumidifier wonít start the problem may be with the humidity sensor. Most electronic control models will use a sensor to monitor the relative humidity which then relays that information to the control board. The control board then uses this information to power the compressor and fan circuits when required. If the sensor is defective it may not correctly measure the relative humidity and therefore not turn the unit on when required. Some models also incorporate a thermistor in the sensor harness that monitors the evaporator temperature as well. Check the harness connections to the control board before condemning the sensor.
Electronic Control Board or PCB
If your dehumidifier is an electronic control model and it wonít start the problem may be with the control board. These models use an electronic control board or PCB to provide power to the compressor and fan motor circuits. If the control board is defective, your unit may not start. The control board is difficult to diagnose and should only be replaced after you have checked all of the other components.