My ac has been loudly humming for the past week... only when it's on... it sounds like its coming from outside... what is this and how can I fix it... thanx:confused:

What kind of AC do you have is it a Room AC or a central AC.

Give us a little ore info and we will try to help.

Make sure your panels are tight. Also if it's a loud squealing noise it could be the bearing on your condenser fan motor going out. Try some wd40 if it still does it, change the motor or live with it until it stops completely. Other than that theirs not much you can do if your compressors loud.

Also if your unit is usually real quiet you might just be hearing your contactor hum. Turn the breaker off to your outside unit and turn the thermostat on cool and see if its still making the same noise.

What tune is it humming?

Most likely if it only makes the noise when its on, and its coming from the outside unit, your compresser is just wearing out, causing it to be a little louder than normal. Not much you can do here, except, clean the condenser coil thoroughly. This won't reduce the noise, but it may prolong the life of the compressor.

Odds are if it is running it is the compressor. Does your unit freeze up?