We just moved into a new to us but 35 year old house. The airconditioning unit is outside and a Carrier - about 5 years old. I can't get the air to turn on. The previous owner has passed away, so I can't ask her any questions. Im wondering if there may be a master switch or something Im missing that may have been turned off in the fall? The furnace switch is on, and the AC breaker isn't tripped. The furnace and blower work fine, but when I switch the thermostat to AC, the outside unit doesn't come on. The thermostat does indicate the AC is running though. So I thought Id ask for any obvious solutions before I call someone in. We didn't test the AC when we bought the house as it was too cold outside.

I blew the 3amp fuse in the furnace when replacing the thermostat with a programmable one. I replaced the fuse and the furnace works fine now. Is there a similar fuse that could be a problem in the outside A/C unit? I have since put the old thermostat back on to see if the airconditioning works with it but no luck. It is wired exactly as it was.

Thanks for any thoughts.

Check the outside disconnect for the unit. It may have fuses/breakers in it. It could also be a defective contactor in the outside unit. Now it could be many more things but the above would be more than likely.

Since you know nothing about how this unit was serviced or if it ever had service I recommend calling a expert to look it over/fix the problem/ oil up the motor and clean the outside condenser. Then they can test the operation and see that it is working correctly so you will have no more trouble this summer.

Check the outside disconnect for the unit. It may have fuses/breakers in it. It could also be a defective contactor in the outside unit. Now it could be many more things but the above would be more than likely.

Since you know nothing about how this unit was serviced or if it ever had service I recommend calling a expert to look it over/fix the problem/ oil up the motor and clean the outside condenser. Then they can test the operation and see that it is working correctly so you will have no more trouble this summer.
Thanks - had someone come in and check it out and do a tuneup on the AC. Turns out it was originally miswired - the AC unit and the humidifier at the furnace. Works great now.