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Old 02-21-2014, 06:53 AM   #1
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What causes blower slow start up on new motor


New blower motor 6.7A 1/3 HP 1100 RPM, new manuf. spec'd 5uf 370v cap (tested at 4.99 uF), which is the specs on furnace data plate, except for the Amps. Data plate amps was 5.8 A., which is what the old motor removed, was... 5.8 A. Standing pilot furnace, no control board

It has the not uncommon start up noise I've heard several times before in these blowers on older mobile home furnaces. Sort of an increasing frequency, staccato patterned hum (vibration?)-type noise that disappears as the motor spins up to full rpm (wa... wa... wa.. wa,wa,wa,wa). Only take a few seconds - 3 to 4 seconds maybe. Maybe the same type sound you hear when a motor won't start because of bad capacitor or failing motor, but increases frequency and disappears as motor spins up.

Squirrel cage before motor replacement was heavily covered with dirt (so was the rest of the furnace - all was cleaned), apparently for a long time. Squirrel cage & blower housing was cleaned. A thin, uniform layer of crust is still on the squirrel cage. Have seen other similarly crusted sq-cages start up without this noise. I usually take the time to scrub a blower wheel clean of any crust, but didn't this time. The crust layer was thin. Wheel was cleaned with 50/50 Clorox/water solution (sprayed on and soaked for a bit) and a hose (rinsed thoroughly & repeatedly), so it got cleaned pretty good.

Voltage at speed selector terminal (in control box, just below Molex connector on top of box) that powers this motor was tested at 120v. Wires from molex go directly to motor.

Motor is generic "#! Source" brand, 3 speed motor purchased for $65.00 + tax, plus mounting bracket and new run cap. Could this motor be reconditioned and weak, or New and bad? Never thought before to ask supplier about status of motor.


Last edited by justplumducky; 02-21-2014 at 07:06 AM.
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Old 02-21-2014, 09:18 AM   #2
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What causes blower slow start up on new motor


the ductwork on trailers is small and the return is a grill in a door. different resistance to airflow than you get with a house furnace so it sounds different.

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