Wiring Done Right

**jeff sr** · 04-14-2023, 04:31 AM

Dehumidifier Not Collecting Water:

Capacitor

If your dehumidifier is no longer pulling water from the air and you have verified that the ambient room or area temperature is above 65 degrees Fahrenheit, then the unit's compressor may not be running. The compressor is the pump that circulates the refrigerant through the evaporator to extract moisture from the air. There is a capacitor in the compressor circuit to help the compressor motor to start and if the capacitor has failed then the compressor won't run. If the compressor doesn't run or if the overload device continues to trip, then you may have a defective capacitor. An accurate diagnosis can be determined by a qualified person using special test equipment.

Overload

If your dehumidifier is no longer pulling water from the air and you have verified that the ambient room or area temperature is above 65 degrees Fahrenheit, then the unit's compressor may not be running. The compressor is the pump that circulates the refrigerant through the evaporator to extract moisture from the air. There is a device in the compressor circuit called an overload and it is used to protect the compressor motor from damage. If the overload has failed then the compressor won't start. If you have verified that the compressor doesn't run, then you can test the overload for continuity with a multi-meter. A common cause for the overload to fail is from operating the dehumidifier on long or undersized extension cords.

Fan motor

If your dehumidifier is not making water and you have verified that the ambient room or area temperature is above 65 degrees Fahrenheit, then you may have a faulty fan motor. For proper operation, a dehumidifier needs to have an adequate amount of air blowing across the evaporator coils to prevent frost or ice build-up. If you feel little or no air coming through the grille area and the filter is clean, then remove the cover and check the fan area. Inspect the coils to make sure that they are not restricted with lint or dirt and clean them if necessary. Make sure that the fan motor rotates freely and that the fan blade or blower wheel is firmly attached to the motor shaft. Using caution, operate the unit in a fan only mode and observe the fan motor. If it hums but does not rotate or only rotates slowly then it is defective and will need to be replaced. If the motor does not rotate and does not appear to make any sound, it may still be defective, but will require further testing by someone who is comfortable with using a multi-meter and working with live electrical circuits.

Electronic Control Board or PCB Assembly

If your dehumidifier is no longer pulling water from the air and you have verified that the ambient room or area temperature is above 65 degrees Fahrenheit, then the unit's compressor or fan motor may not be operating. The compressor is the pump that circulates the refrigerant through the evaporator, and the fan motor blows air across the evaporator coils to extract the moisture. On some modern dehumidifiers an electronic control board, often called the PCB, is used to control the compressor and fan motor. The control board has sensors connected to it that monitor the relative humidity and when the level is higher than the control setting, the control board will activate relays to turn on the compressor and fan motor. If you have an electronic control model and the compressor or the fan is not operating, then the electronic control may be at fault. A voltage test, using a multi-meter at the output relays, would be required to help in the diagnosis as well as confirmation that the sensors are operating normally.

Dehumidifier Keeps Shutting Off:

Sensor

If your dehumidifier won't stay running, then 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 electronic control board. The control board then uses this information to power the compressor and fan motor circuits when required. If the sensor is defective it may not correctly measure the relative humidity and therefore may turn the unit off before the set level is reached. Some models may also incorporate a thermistor in the sensor harness that monitors the evaporator temperature as well. A defective thermistor may cause the unit to shut down prematurely as well. Check the harness connections to the control board before condemning the sensor.

Humidity Control or Humidistat

If your dehumidifier won't stay running or shuts off too soon, the problem may be with the humidity control or humidistat. The humidistat monitors the relative humidity in the air and then supplies power to the compressor circuit when the humidity level exceeds the user's set point. If the control does not sense the relative humidity correctly then it may shut the compressor off prematurely. It is difficult to test the control unless you have a hygrometer to accurately measure the relative humidity of the room. If you have to adjust the control to a setting lower than normal to keep it running and the relative humidity of the room is consistent, then you may have a defective humidistat.

Dehumidifier Will Not Turn On:

Float Assembly

If your dehumidifier won't 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 won't start, check the operation of the float to ensure that it moves freely and contacts the level switch properly. Make sure the holes in the bucket for the float are not elongated or worn too big.

Humidistat

If your dehumidifier won't 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 user's 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.

Sensor

If your dehumidifier won't 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 won't 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.

Continued on page 3

jeff sr.

**jeff sr** · 04-14-2023, 04:32 AM

Auto Shut Off or Bucket Level Switch

If your dehumidifier won't start the problem may be with the automatic shut off switch. Sometimes referred to as the bucket switch or water level switch, it is a safety device to prevent the unit from overflowing. The switch is located near the bucket and is tripped by a float mechanism when the water level in the bucket rises or if the bucket is not in the correct position. When the switch is tripped, power to the compressor and fan motor circuits is disrupted until the bucket is emptied or properly positioned, and an indicator lamp or display should illuminate to tell the user of the status. If your dehumidifier won't start but the bucket indicator light or display is not on, you may still have a problem with the shut off switch. Verify that the bucket is not full and that it is in the correct position and also check the float assembly to ensure that it contacts the switch properly. You can test the switch for continuity with a multi-meter.

Refrigerant gas information:

The refrigerant denotes the liquid contained in the evaporator coils, which helps to trap moisture from the air circulated within the dehumidifier. Therefore, it's safe to assume that without the refrigerant, the dehumidifier cannot function. While coils are designed to resist leakage, the refrigerant's vibrations and progressive ageing of the equipment can cause perforations and breakage, which can lead to refrigerant leakage. When these tiny holes go undetected for long, the refrigerant might decrease to low levels. This, in turn, reduces the ability of the dehumidifier to collect water.

This is an example of a major system problem like a leak in the refrigeration system. This could also be an inefficient or weak pumping compressor.

This is an example of frosting or freezing up on the evaporator coils.

This is an example of a major system problem like a leak in the refrigeration system. This could also be an inefficient or weak pumping compressor.

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