My Whirlpool 6th sense split type air conditioner doesn't cool.Everything lights up as always and the red indicator inside shows the compressor should be running.Outside the fan is running.When I stand outside by the unit every 10 seconds or so I hear a relay click followed by a 5 second humming sound then the relay kicks back out and this will continue every 10-15 seconds.Something(the compressor?)is trying to engage but all I get is the humming.This is the same hum I've heard on other electrical devices when a motor tried to turn but was frozen and couldn't.I was an auto mechanic and the humming meant something wasn't turning and the high resistance caused the relay that turned it on to kick back out to avoid overheating or a fire hazard.I can take the covers off the unit very easily but what am I looking for? The unit itself is only a few years old so it's not worn out. Help please!!!

It is possible you have a

Bad start relay if present in your system.
A defective start capacitor if present in your system.
A defective run capacitor
A defective compressor.
A loose or burnt wire in the system or on the compressor itself..

These are just for starters. You will need an electric meter and real capacitor testing tool (since a OHM meter will not tell the true value of a capacitor) and follow the wiring diagram on the inside of the service access panel. If you do not have the experience of working on a HVAC unit I suggest you contact a HVAC professional for this work. The items you will be testing are somewhat complex and the information needed to do this job cannot be learned on a forum such as this in short order. Good luck with your repair.