Charge level issues with dehumidifier s

Question about characteristics of proper charge on a dehumidifier. I have 2 malfunctions dehumidifiers (one 2 months old, one 2 years old, both given to me
with no warranty info) with basically the same symptoms.: when running, they ice up starting from where the capillary tubes enter the evaporator and the first part of the evaporator. Sounds like low charge. No evidence of leaks (oily spots) but the thing that confuses me is that the hp lines and the compressors get really hot, to the point where the newer one shuts off ( overheat switch in the compressor) . And yes, the fan/airflow is fine over both the condenser/and evaporator. So the hot and overheating part confuses me. Also, neither have ever been serviced or opened up before. Not sure if these are worth investing $150 into a tank of 410a and a couple piercing valves or not, if even low refrigerant is the issue. Any thoughts?
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