A/C Fan won't turn on outside after replacing capacitor

Question

I know this is a DIY stack exchange, and to be forthright, I did not DIY this initial repair because I was intimidated by replacing a capacitor, so I called a recommended technician who did the job and got the A/C running immediately. I am posting to this forum because we have a new problem and I'm trying to understand how it might be related to the initial one.

So, the initial problem was that I noticed the air blowing was not cold, and the fan was not running outside although the compressor was on. I guessed it was the capacitor based on research but didn't want to mess with that because I don't do a lot of electrical work and my dad was visiting in town, so I needed the A/C fixed quickly. The tech came out, tested our dual capacitor and found that the fan side was not responding, and replaced it with a new capacitor. The a/c was up and running again. It cooled just fine that evening, and I raised the thermostat a bit to 76 so it would shut off and went to bed.

Then early the next morning, I heard the a/c making an intermittent buzzing noise (it's outside our bedroom window) and could hear the air blowing in our house. It sounded like the unit was trying to turn on the fan but couldn't. My husband went out there and tried to spin the blade but couldn't get it to start and noticed it was hot. So I turned off everything and put in a call to the tech - I'm waiting for him to call back right now.

My question is: what could the problem be? Is it related to the new capacitor? My hunch is the fan motor, but I don't know why it would be working just fine up until last night and then suddenly fail. Thanks for any help or insight you can provide.

Answer 1

Having a bad capacitor can put an extra strain on the motor. An AC is actually a pretty simple device when it comes down to it, so the only replaceable parts (in this situation) are the fan and the capacitor. Some units have a control board that handles some timing and sensors. That can go bad but it's not as common (in my limited experience anyway). If you hear the compressor coming on and the fan trying to start, then any control board is probably OK.

So possibilities:

• The fan is in bad shape and somehow blew the new capacitor
• The fan was damaged by the previous bad capacitor, ran for a bit, but now won't even start with a good capacitor
• The new capacitor was just a dud and failed almost immediately

If you had a multimeter, you could check the capacitor and also check the resistance of the fan motor windings as additional troubleshooting steps.