Usually, a dehumidifier ices up because of two things, poor air circulation and operating in low temperatures. Refrigerant dehumidifiers are the usual culprits of coils developing ice. Running it at below 65°F can be an issue.
Other reasons include:
- Using the wrong humidity sensor
- Using a Bi-Metal Thermostat that isn’t working
- A broken blower wheel or fan motor could be the problem.
- Clogging of the air filter.
- The evaporator and condenser coils could be dirty
- There is airflow obstruction.
- There could be other mechanical or electrical problems
- There is a warning light on your dehumidifier that you have ignored.
Common Reasons Why Dehumidifiers Ice Up
Air Circulation problems
One reason your dehumidifier may be freezing is airflow blockage. If something is keeping the fan from working or if the condenser clogs, you will have an airflow issue. You can avoid such problems with regular and proper dehumidifier maintenance. It will also assist you in determining the root of the problem sooner. As a result, you can clean or replace the part as needed.
The temperature factor
It’s possible that the temperature of the room where your dehumidifiers, is causing it to ice up.
When the temperature is lower, the water vapors may freeze rather than condense. As the vapor freezes around the coil, it disrupts ventilation. Your dehumidifier will stop working, this causes problems.
What Happens When A Dehumidifier Ices Up?
Cold evaporator coils, warm condenser coils, a fan, and a reservoir or drain are in a dehumidifier. It also comes with a humidistat, which works to a thermostat. It cycles your dehumidifier based on the level of humidity in the room.
Air goes into the vents of your dehumidifier. After that, the air passes through the cool metal coils. It condenses it and turns it into water droplets. These droplets are either kept in the reservoir or pumped through a hose. This depends on the sort of dehumidifier you have.
The droplets do not reach the reservoir when your dehumidifier freezes. Instead, it blows a chilly breeze. When the temperature rises and the ice melts, the reservoir overflows. This poses a risk to your humidifier. In the summer, this is a common occurrence. 
Side Effects Of A Iced Dehumidifier
- Damaged parts reduce the life expectancy of the product.
- To absorb the surplus moisture, the fan motor and compressor will have to work harder.
- As wear and tear parts continue, there will be more rattling noise or vibration.
- Dehumidification output drops as the coils become more clogged.
- Your electricity expenses will increase as you extend your running hours. This will be due to lower performance.
- Continuous use poses a fire threat.
How to Troubleshoot A Dehumidifier That Is Icing Up
There are four steps you can take to troubleshoot a dehumidifier that is icing up. Here they are:
Place the dehumidifier in a location with at least one foot of clearance. It allows for proper air circulation while it is operating. Ensure that your unit isn’t attempting to remove moisture from outside of the room. Close all windows, doors, and other outside openings.
Check a nearby thermostat. You can also use a hand-held thermometer to determine the room’s air temperature. If the temperature is over 41 °F, some Frigidaire models can run without freezing. Some Soleus devices may work at 36 °F. If the temperature falls below these levels, turn off your unit. Only switch it back on when the temperature rises above these levels.
Remove any debris or debris from the filter. Remove the unit from the power source and open the filter container to inspect the filter. If the filter is unclean, it will restrict airflow through the device. This results in it freezing. To remove dirt from the filter’s surface, Soleus recommends vacuuming it. If the filter is filthy, you can also wash it in warm water. Replace the filter in its chamber once you clean it. Allow the ice to melt before turning on your dehumidifier.
Elevate the unit off the floor to take advantage of the warmer temperatures. Unplug the dehumidifier and drain the tank of water. Place the unit on a firm table or surface. Once the frost or ice has melted, replace the tank. Then reconnect the device to a power source, and restart the dehumidifier. 
How To Fix or Repair A Dehumidifier That Is Icing Up
As before indicated, check the temperature of your room. The dehumidifier will freeze if the room temperature is below 40 °F . An evaporator coil that is fully frosted is clear evidence of this.
If you think your room is too cold, place the dehumidifier on a table to circulate somewhat warmer air. If it doesn’t work, try directing a tiny fan or heater toward the unit. If that doesn’t work, attempt boosting the room temperature somewhat.
Check to see if the fan is operating. The dehumidifier will freeze if you don’t hear the fan moving air across the coils. This is especially when the device is on and running.
If it has a filter, clean it. If your dehumidifier has a filter, clean it according to the manufacturer’s instructions. In most cases, use a vacuum cleaner, though you can clean foam filters with a faucet spray.
You should vacuum condenser coils. The coils inside the unit cannot function well if they are unclean. Remove the screws that secure the outside shell of the dehumidifier and unplug it.
If the coils are totally iced up or only partially iced up, make a note of it. Low refrigerant or a faulty compressor is likely to blame if only some areas of the coils have frost.
Allow all ice to melt and any extra moisture in the coils to evaporate. Then, using a vacuum cleaner with a brush attachment, remove all dust buildup. This takes care not to harm the coils.
Take the unit outside. Cover the engine and electrical parts with plastic sheeting. Then spray the coils with water if vacuuming the coils doesn’t get them clean enough. Drain the unit and allow it to dry before reassembling and connecting it in.
Run the unit through its paces. Turn the dehumidifier on after plugging it in to see if it freezes up again.
Make a choice. If it still doesn’t work, it’s most likely due to a low refrigerant level. You must now decide whether to take it to an appliance repair shop or throw it out and buy a new one.
Get an estimate of the cost of recharging and/or fixing your dehumidifier before taking it to a repair shop. Then decide whether it is worthwhile.
Consider Buying A Low-Temperature Dehumidifier
If your dehumidifier is icing is not something for you to panic about. There are several possibilities that it could happen. But this is a problem you can resolve yourself. Follow the steps and you should be back in business. Or look for a dehumidifier that can work in low temperatures or one with Auto-defrost features.