My Ducane a/c won't turn on.?

The blower works but the outside unit wont kick on. It just hums. It worked yesterday (90 degrees so it was running a lot. But later in the evening it wouldn't turn back on. I pulled the access panel off and didnt find any burnt wires, the contactor looks pretty clean, the capacitor has rust all the way around it except for the top where the wires plug in. I wiggled all the connections to see if one was loose, but nothing. After that i kicked it back on to where it was humming and gave the fan a little boost to start it and it kicked the fan on and it was running but the air in the house wasnt cold. (It was almost 80 in my house all night.:0)

Anybody got an idea? Is my fan motor junk or soon to be junk? Is there a way to test the contactor or capacitor? Is it something else?