The other day my AC stopped working. I'm thinking the condenser fan motor has gone bad (unit is ~10 years old). Here is what I did to troubleshoot which led me to believe it was the fan motor.

1.Turned on, sounds like the compressor kicks on, but the fan doesn't turn on.

  1. I turned the power off and took the top grate off. The fan blades turn just fine.

  2. I took the side panel off and all the wiring looks good.

  3. I disconnected the fan from the defrost circuit and tested continuity on the two terminals on the defrost circuit (while thermostat was set to cool, temp was way down, but power was still off). Had continuity.

  4. I bypassed the defrost circuit by hooking the two wires together and turned power on. Compressor turns on, fan does not.

  5. I checked the contactor to make sure no wires were loose and look for corrosion. Everything looked good. In fact, with thermostat set to cool and temp turned down (high voltage power off), the contactor's electromagnet was working and the switch was on.

Basically I followed the instructions here, which incidentally, the unit they are working on is identical to my unit, which was nice. The only thing I didn't check was the capacitor as I don't have a multimeter which checks farads.

I'm going to check the capacitor tonight as I'm borrowing a better multimeter from a friend. Assuming that checks out, does my diagnosis sound good?

Do I need to change the capacitor too?

Being a ~10 year old unit, I'm aware that I'll probably need to replace the whole thing soon. I'm hoping a new fan motor will buy me a few years though. If not, I'd rather waste $100 instead of $200 trying to replace the motor.

Based on the info in this question, I decided to fire up the AC and give the fan a push. It started right up. I got my friend's multimeter, but it only went up to 20μF. My capacitor said 40μF, so I didn't test it. Since spinning the fan blades with the AC on got it going, I'm going to replace the capacitor today.

marked as duplicate by HerrBag, auujay, ChrisF Aug 21 '13 at 21:47

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • 1
    I would test the capacitance of the fan capacitor (or the fan-side of the capacitor), after following proper safety precautions, before I go to the conclusion of a bad fan. Capacitor = $10-20, Fan = (you've seen). – Jacob S Aug 14 '13 at 19:29
  • 1
    My answer to this question might be helpful. – Tester101 Aug 15 '13 at 12:00
  • And replacing the condenser fan capacitor fixed the problem...right? Good diagnostics on your end! – Richard Raustad Aug 16 '13 at 2:22