Dehumidifier frosts up

A dehumidifier will often frost up if room temperatures are colder than about 65 degrees F. If your room temperature isn't this cold, airflow to the unit may be restricted or blocked entirely.

1) Be sure the unit is set far enough from the wall so that airflow isn't restricted.

2) Clean the evaporator coils. To do this, unplug the dehumidifier and take off the outer cover. Allow excess moisture to evaporate from the coils. Then, using a brush attachment on a vacuum cleaner, remove all dust buildup. If necessary, cover the motor and electrical parts with plastic sheeting and spray with water.

After ice on the coils and outside top of unit was thawed we cleaned the unit and waited 2 days then put the unit back together. After plugging the unit in and turning it on, "ON' came up in the humidity setting window,but when we activated the up or down buttons on the humidity contol the % numbers did not appear in the window-- only "ON" remained. We ran the unit for a while and again the outside top front of the unit felt very cold and we were concerned that it might freeze-up once more so we turned the unit off. We would appreciate any suggestions.

I agree!

Also, another problem that could cause the unit to frost up is that it might be low on freon.

If you've ever had an air-conditioner frosting problem, then you'll understand. Freon is a strange element! I won't go into a lengthy explanation here, but if there is too much freon in your unit, it will not cool optimally, & if there is too little, it'll cool too well, causing frosting on the coils & the condenser.

A dehumidifier is basically an air-conditioner, as it has freon in it. By lowering the temperature of the unit's coils, it causes excess moisture in the air (humidity) to condense on the cools, where it can be channeled into a recepticle & removed.

Unfortunately, the cost of having the freon checked & (if necessary) replenished, would be too high to justify in a 'cheap' unit, such as a window air-conditioner or dehumidifier.
So, if none of the above 'fixes' works, then your unit is probably low on freon (has a slow leak) & your best bet would be to replace it!

Replace the auto defrost thermostat

Clean the filter. My unit had the same symptoms and my filter was completely obstructed. It slips out and you can wash it and than let it dry.