blower fan hums and trips limit switch

[cesmith062851]

Blower motor housing model #900759

I am having to reset the limit switch for the burners to kick on...but now, after resetting, fan motor just hums and does not run.

My assumption is the motor is bad. Good assumption or bad. Thanks in advance.

Craig Smith

[Robert]

Hi,

Never reset limits without first repairing the problem, resetting can make them weak and inoperable.


Set t-stat to call for heat and when blower should run, spin the blower wheel in correct direction and see if it starts up and runs.


Could be motor, run capacitor or wiring problem.



Thanks,
Robert

[cesmith062851]

Hi Robert,

Thanks much for the quick reply!

Yes, the motor runs slowly to begin with after I spin the wheel and then spins freely.

Should I try changing out the fan capacitor?

Thanks again.

Craig

[Robert]

Hi Craig,


You would have to replace the run cap any way if the motor is bad. So go ahead and see if that works.


Can give ordering info if needed. Will need same mfd rating and same voltage or higher rating.



Thanks,
Robert

[cesmith062851]

Hi Robert,

Hey thanks a bunch! That's kinda what I figured.

I ordered a 10mfd 370VAC from your online parts catalog. I cant' read the rating on the existing run cap but thought the 10mfd would be equal to or higher rated than the exising.

Thanks again. I really appreciate your input.

All the best,

Craig

[Robert]

Hi Craig,

What is your furnace model number ?

Do you have heat only or heat and a/c ?


MFD rating MUST be same, voltage rating can be same or higher.


You can call toll free to 1-877-263-7860 and cancel order until we verify correct run cap.



Thanks,
Robert

[cesmith062851]

Hi Robert,

Furnace model number is 7900. Heat and A/C.
My mistake....I thought the mfd rating could be the same or higher not the voltage.

Also, the blower housing is a Nordyne model 900759...if that helps.

Thanks!

Craig

[Robert]

Hi Craig,

Look on furnace facing for data sticker or nameplate to get furnace model number. 7900 is just a series, the model number will be something like 7956-856 .


Need complete model number.

They change p/n's constantly and the furnace model is needed to get new p/n.


Thanks,
Robert

[cesmith062851]

Hi Robert,

The model number is 7956A856.
BTU input 56,000
BTU output 46,000

BTW I did call the office and ask them to hold the order but I thinked it got shipped anyway. No big deal....we will work it out.

Thanks for all you do!

Craig

[Robert]

Hi Craig,

The 10mfd / 370V is correct run cap, so call back tomorrow toll free to 1-877-263-7860

and see if it was shipped. If not, reorder it .


Take care and best wishes,
Robert

[cesmith062851]

Hi Robert,

Hey...great...lucky guess on my part.
I will call to confirm order.
Thanks again for all your help!

Merry Christmas!!

Blessings,

Craig

[Robert]

Hi Craig,

You're very welcome, happy to help. Merry Christmas to you and yours !!


Take care and best wishes,
Robert