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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8675
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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How to trouble shoot blower motor? Was working fine but will

Customer Question

How to trouble shoot blower motor? Was working fine but will not start now. you can hear a "hum" when you bump the t-tstat. Where do I start trouble shooting? Thanks in advance!!
JA: I'll do all I can to help. How long have you been dealing with this?
Customer: I noticed yesterday that the blower was not starting up so I just shut down the system. About a week ago a tech came out and add freon to the system. Everything was cooling perfectly for a few days, up until now.
JA: Do you plan on doing the work yourself?
Customer: If possible. I'm more than capable and I believe it might be something that's easily repaired. With that being said I know when to say nope that's above my head because Heat pumps/AC units are like vehicle transmissions - there are no cheap mistatkes!! lol
JA: Did you double-check the thermostat's settings? And what about the filters?
Customer: Yes all of the simple/common things. The cap to the blower went out when the system was around 5 yrs old and I replaced it. The current symptoms are vary similiar. System is approximatley 11 yrs old now. I have a spare cap and tried it but still the same. Coil comes on, outside unit/fan comes on - just no blower.
JA: Anything else we should know to help you best?
Customer: I think thats it.
Submitted: 4 months ago.
Category: HVAC
Expert:  Phil replied 4 months ago.

Hello,I am a retired mechanical engineer with 56 years in this business. I will go in depth with you, and up to a 6 hour time limit.

All I ask is please select the ***RATING LINK*** at the top of your page before leaving, 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 can agree to that, lets continue by all means.

I need the brand and model number of your furnace to determine if its a variable speed motor, or a 3 speed motor. If its a 3 speed motor with a cigarette sized metal capacitor mounted on the blower housing, replace the capacitor... take it to Grainger industrial supply or Johnstone Supply for a match up, if that fails the motor is bad.

IF the motor is a variable speed type things get a lot more complex, tell me a lot about your technical skills so that I can coach you most effectively. Variable speed motors have no capacitor and they have 8 to 14 wires attached to them instead of just 4 wires.

We can go from here when I get back from lunch or you can opt me out if you do not want to wait.