Central air outdoor fan won't turn on

I have central air in my home. I tried to lower the temp last night to 73 degrees (it was set at 75 degrees). The outside air conditioning unit ran for a long, long time. There was an electrical storm last night as well. This morning the outside unit's fan will not go on. It's making a funny high pitch sound and then it sounds as if air is escaping, or hissing. It's extremely hot as well. I suspect the heat is due to the air condenser or the air compressor overheating. The inside blower fan works fine but needless to say the air is not being cooled. I turned off the air conditioner for a while to cool outside unit off and turned it back on after about two hours but that didn't solve anything.

Can someone tell me how to diagnose the problem? I suspect it might the capacitor but I'm not certain. Thanks.

 

A quick & dirty way to diagnose a bad capacitor is to turn the unit on & give the fan a spin with a small stick. If the fan starts & runs for a little while, the cap is likely bad.

 

Thanks Grady,

I didn't unscrew the top but I tried the 'stick' test earlier by poking the stick through the vents in the top and trying to spin it but it didn't take off. It spins rather freely however, I couldn't get much force behind it due to the narrow vent slits. I'll try it again in the morning. I'll unscrew the top and try to spin it. What if it spins but doesn't come on, what's the next likely step? I appreciate your help.

Thanks again, Ed.

 

If it spins freely but does not take off check the wiring to make sure there is not a wire broken or burned off. If you have a multi-meter & know how to use it, you can check for voltage to the fan motor ((+/- 230 volts). A further test would be ohms from each of the fan motor wires to each of the other fan motor wires.

 

Thanks so much Grady,

Tested the voltage on the condenser motor and found it wasn't getting the correct amount. It's probably burned out. It's old and the electrical storm or lowering the thermostat may have finally killed it. Removed the motor and now I'm going to replace and remount it and hope I've fixed it. This is great site and has probably saved me hundreds of dollars. I'll let you know after I've installed it tomorrow if it's working. Thanks again for your help.

 

If the correct voltage was not going to the motor, you need to find out why. You could damage a new motor. I suggest replacing the capacitor first. They are inexpensive & available at any electric motor shop. If you do replace the motor, be sure to get a new capacitor properly sized for the motor.