My a/c unit will not turn on. It is fine at the thermostat and the blower fan turns on but the a/c unit outside will not turn on.
First check the disconnect/circuit breaker that should be located close to the outside unit. Next remove the cover where the power goes into the outside unit so that you can see the contactor. Do a visual check of the contactor and contacts. Set the thermostat to make the A/C come, then look at the contactor to see if the contacts have closed. Use a voltmeter to check for power on the load side of the contactor. If the contacts didn't close, remove the thermostat face and install a jumper between R and Y terminals and see if it pulls in then. If it does then, the problem is your thermostat. If the contacts close and you have power check the capacitor next. If it looks swollen, it is bad - replace it, otherwise you can check it with a multimeter with the capacitor check function. Try these simple checks and let me know what you find if this doesn't fix it so I can give you some more things to look at.