My compressor never shuts off. I have set it as high as 78 and it keeps running. The room is well into the 60's.

Possibly a tstat issue. Run system until satisfied, once satisfied indoor fan shuts down compressor still runs remove tstat face plate and see if compressor shuts down. Another issue could be a sticking contactor for compressor. With a meter you could check at the contactor to see if you lose your 24volts for cooling but contactor remains pulled in.

Normal ACs (non inverter) work in the following way

• The AC compressor runs continuously till set temperature is reached in the room
• The compressor then switches off, but the blower fan in the wall mounter unit keeps running. Durint this time the AC fan blows air out at Room temperature (which feels warmer)
• When temperature of room rises then compressor starts running again. During theis period the air coming out from the inner uny is cooled by the condenser coils
• And the process is repeated.... as long as you keep AC running

Ac works this way throught the operation period.
Now if you feel that your AC keeps switching off and on very frequently check the following

• Your AC may be over powered for room *for example a 1.5 ton AC installed in a scenario where 1 ton is enough)
• If there is voltage fluctuation in your area then the compressor may keep shutting don on large voltage swings
  • Solution: Get a Stabilizer
• You have set the temperature setting too high. Max temp suggested for ACs is 25 degree Celsius, any higher will mean the compressor shuts down often. Remember every compressor shutdown and startup draws a high starting current
  • Set AC temperatures between 22 and 24 degrees Celsius
• The thermostat/ Temperature sensor is faulty
  • Get unit inspected by Authorized technician
• There is dust buildup on the outer unit / compressor unit. The dust buildup may cause overheating by preventing efficient heat exchange, This may lead to overheating of compressor and it shuts down to, prevent damage to itself
  • Get unit serviced by Authorized technician
• The fan motor of the outer unit is not working properly
  • Get unit inspected by Authorized technician

Remember to get the AC serviced at least thrice a year to ensure smooth operation
Cool Thoughts... Cool Life !!!

if it is an inverter type air conditioner ( make not indicated) the unit runs continually but the compressor delivery is reduced thereby reducing the load on the motor
as the room warms up again the compressor starts to pump more gas to keep the room at the desired temp setting
older types shut the compressor down and restarted when the high temp was reached

Verify the humidity reading with another device. Perhaps the humidity sensor is dirty or bad.

Another possibility is the switching device that runs the compressor and fan is shorted. If it's a mechanical relay, the contacts may have welded together, or if it's a solid-state relay, it's got a punch-through or meltdown in a device junction. My guess is it's a mechanical relay since you mention it used to click on and off and now you don't hear that. The relay may be on the control board, or it may be mounted separately - I don't have a photo or diagram of the inside of your model available.

The thermostat has a differential built into the temperature sensing operation. The differential is normally a degree or more. If the stat shuts down at 72 degrees it should not start the unit again until the temperature in the room reaches 73. If the AC runs and cools properly until it shuts down, I would check the thermostat. The AC can not restart immediately after it shuts off because the pressures in the system are too high at the compressor. It takes a few minutes for the pressures equalize allowing the compressor to start. If the stat tells the unit to start under high pressure, the compressor will shut down on overload. It will start and run after the pressure falls enough for the compressor motor to run.

The compressor cannot shut itself off. Why do they say it's the compressor? The control circuit shuts off the compressor if the pressures are off or the inside temp reaches setting. Did the mechanic check the pressures, high and low?

Most likely is a issue with the temperature sensor that when it reaches the level selected is not turning the compressor off.

If your unit is running 24/7 you are either low on charge or the unit is to small for your house.
A 20° temperature difference is about normal for the room air vs the air coming out of the ducts, but the room air and the leaving air should keep getting colder and colder.
An air conditioner should cycle approximately 3 maybe 4 times in an hour if it's properly sized.
As for the thermostat thermometer they are very cheap and are more for reference than actual temperature, so if 78° is not comfortable, then you should set it lower but not rely on thermostat being accurate or what the thermometer is saying as long as it is consistent.
The air conditioner and thermostat can also be set below 78°, there's a lot of people set them at 72° and below with no problems.
the only thing is if you have real low humidity you'll need to watch indoor coil or the suction line (the big line) on your outdoor unit and make sure it doesn't freeze up on you.

low on freon is the compressor running?

I just bought the LG 10000 btu window model... I am having the same exact problem.. it feels like the air is not even on.. I am having someone look at it on Mon. I have a feeling the whole unit is defective. But it could be the thermostat needs to be replaced. Sucks 300 dollar brand new AC and it doesnt work!! Good luck. I will never buy LG again.