The compressor always stop. how can i feel the compressor?

I would say low on gas or bad switch/thermostat.
The compressor probably has a shutoff for low freon. You would need a set of gauges to check for that.
Bad thermostat? You'd need a ohm meter.
User error? What kinda settings or controls do you have on the control panel?
There was a recall on these in 2014 for catching on fire.
Gree Reannounces Dehumidifier Recall Due to Serious Fire and Burn Hazards...

Lyle, your particular model is designed for the fan to function constantly. However, the fan running doesn't mean the compressor is always running. The reason the unit was designed this way, is for the air to be continually moving, and when the humidity sensor picks up a rise in the humidity level (above where you have it set) the compressor will turn ON and extract that humidity.

Your unit is working as it should. Thanks for choosing FixYa.

Are you sure it is the compressor and not the condenser fan? Check the compressor vibration mounts to be sure they are OK. Feel the in and out lines of the compressor (be careful) the out should be almost to hot to hold and the in should be cool to cold. If this is true then the probable solution is to replace the compressor.
Good Luck,
Gilshultz

Assuming there is moisture in the air, it could be several things. Be sure the unit is clean and the compressor and fan are running. If not it probably is the humidstat. The outlet line from the compressor should be warm and the return cold. If they are not and the compressor is operating you either have lost refrigerant or the compressor has failed.
Good Luck,
Gilsh

the compressor has an internal overload to protect it from overheating. the compressor is cooled by the refrigerant passing over it. It could be a bad compressor,, bad charge of refrigerant, or simply dirty coils not allowing air movement

A dehumidifier is basically an air conditioner, so some coils should feel hot, the others should feel cold.

If no water is collecting, then the unit's compressor is not starting. Typically you have four possible failures causing this: the switch/wiring for the compressor has an open circuit, the motor-start capacitor for the compressor has failed, the compressor itself has failed, or all the refrigerant has leaked out.

If there is evidence that it is 'trying to start', but then clicking repeatedly, this can be a symptom that the refrigerant has leaked out, as some devices have a pressure switch to prevent compressor damage.

Also, a failed start-capacitor can also cause the click-click noise if the device has a current limiter switch on the compressor.

So the short answer is, it's broken :)

fan should turn off when compressor not running, the relay switch is stuck open for the fan, and probably needs replacing, but even if it always runs there is no harm and it only uses like 15 watts

Try to feel the lines on the compressor. The thinner line is High press and should get hot. The fatter line is Low press and should feel cold. Cold enough to allow water vapor to condense on it and turn into droplets. If neither occurs, compressor has lost "freon" charge.

I have AD75USTO. Whirlpool  was running yesterday. Today it sound like its starting but will not boot up fan will not kick on. Does it need resetting or what. Only a year old only used for one summer?

attempt to feel the metal fins on the back of the unit. If they do not feel cool, then unit is either out of freon or compressor has failed or compressor is not running. If fins are cool, then insufficient air flow through unit -check fan- or room has very low humidity and humidistat is defective; not shutting down compressor.