I came home from work day before yesterday and found a house very hot even though the air conditioner was set to be running. Upon looking at the outside unit I found it humming but neither the compressor nor the circulating fan running. The humming of the motor indicated to me that it was trying to run but was having difficulty doing so. I killed the power and opened up the control side and checked the capacitor. I found it it was swollen and out of shape which is an indicator that it is bad. Sometimes they were rupture other times they will look fine although they are bad. If it is not physically altered you may have to take it to a air conditioning supply house to have it checked for you. The capacitor cost me approximately $18 and is quite simple to change out. And could save you quite a bit of money on a service call and mark up from an HVAC contractor
