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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8768
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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What can cause a fan on the AC to run backwards, week, yes,

Customer Question

what can cause a fan on the AC to run backwards
JA: I'll do all I can to help. How long have you been dealing with this?
Customer: week
JA: Do you plan on doing the work yourself?
Customer: yes
JA: Anything else we should know to help you best?
Customer: I can hear the condenser run but the fan is running the wrong way. the capacitor has been changed
Submitted: 3 months ago.
Category: HVAC
Expert:  Phil replied 3 months ago.

The condenser motor is either wired incorrectly, which could be the case if it is a replacement... or the motor is going bad.

The blade should run so that the lower edge of the blade moves in the direction it is pointed in.

It is also possible that the blade was installed upside down, or if it is a new blade that it was purchased incorrectly.


I am a retired mechanical engineer and HVAC/ electrical/ refrigeration and boiler contractor ... with 56 years in this business.


The last 20 of those years consulting for major firms nationally..All I ask is please select the ***RATING LINK***at the top of your page, that is the only way I am credited through the site.


Rating does not affect your charges nor ability to refund if not satisfied..


If you need to be coached through a full diagnosis/repair, and wiring etc. for up to two days, and wish to be trained to use test instruments...... that goes well beyond' Just a simple Answer' of course.. ..


Rate my simple answer so far positively..and I will deliver that training and coaching to you All on the same dime so to speak..


If you can agree to that, rate now, lets continue by all means.

Customer: replied 3 months ago.
The fan Has not been replaced or replaced, so the fan could be bad, Ha!
Customer: replied 3 months ago.
No! I can do the replacement of the fan!
Expert:  Phil replied 3 months ago.

Send me a photo of the fan blade inside the unit so that I can hopefully see it clearly enough to tell which way it should be rotating. We do not want to get this wrong.

Use the 'add files' link next to your send button for that.

Once we have establisihed that the fan motor is bad, take it to Grainger Industrial Supply or Johnstone Supply for a match up, get a new run capacitor for it as well.

Expert:  Phil replied 3 months ago.

If you want further coaching on this, and help wiring the new motor (which the wiring will be slightly different ) rate my work so far positively. Or if you wish I can opt out. Its entirely up to you.