Air conditioner not getting cold

Yes. due to low rpm of fan motor in the condensor copil. or dirty condensor coil. I If so, replace fan capacitor.
If all good, check the seating of condensor set. It needs minimum 2mtrs open space for air throw. If not due to overheat compressor gets short cycling on and off.

Sounds like the thermostat, the way to verify is to unplug indoor unit, remove thermostat, take pic of wiring with phone or label the wires as to the terminals. Carefully twist the yellow,(Y) Red (R) and the green (G) together. Plug the furnace back in, if the unit operates normally, replace the thermostat. I am basing this on the fact that the blower speed is changing. This could also be an anomaly within the circuit board in the furnace section, not likely though as the outside unit (condenser) is not controlled n by the indoor board unless this is a heat pump. hope this helps. D

Before I even read that far into your post, I was thinking "thermostat" replace it...It seems to be failing badly. If you take it into logical perspective...normally the unit gets turned on, then takes a bit to get cold, then once it reaches its pre-determined temperature, turns the unit either "off" or just blows the fan...by kicking off the compressor. This unit you have is getting this cycle done within 5 minutes instead of a few hours...replace the thermo and you should be fine. Now if you could post the exact model number here I can go look up the part for you.

HMMM this sounds like a couple things possible Low voltage due to lose wiring some place. or low voltage due to the power company . something is pulling more amps than it should.

do you have an automatic change over thermostat? this would switch it from heating to cooling.

most like it the motor windings are burn and you need to replace the blower motor

This could be an inoperative condenser fan.System will kick off on high pressure without proper air flow.The hum indicates voltage is present. Providing the fan motor is not locked up and will spin,Check your run capacitor which helps boost the motor voltage initially and will get it turning.If the cap is good,you may be faced with motor replacement....good luck

What type of thermostat are you using? When was the last time it worked ? Do you just get fan on cool mode, or does fan only run on fan mode?

If it's in Energy Saving mode, that may be normal.

Geno

it has very low amount of freon left. best economical decision is replace unit.