hvac blower motor intermittent

My house has a Friedrich brand furnace about 25 years old or so. Sometimes I run the blower continuously (that is, not under control of the thermostat) just to keep the air circulating in the house--neither heating nor cooling active. Recently the blower motor has been cutting out. The motor will just stop for several seconds and then restart itself. Since this is probably not good for the motor, I have stopped running the blower continuously.
Just wondering if there are is a typical cause for this. Do I need a whole new blower or can I easily repair this motor by installing new brushes or some such thing?
Thanks for any input.
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If the motor is stopping on its own, it sounds like it is shutting off due to the thermal overloads inside the motor. This can be for a lot of reasons. Replace the air filter, clean everything that you can before the motor location. Check to see that the motor has the cooling vents open and operational. Failing all of this time for a new motor.
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I doubt this caused by overheating - the internal overload wouldn't normally reset that quickly. More like electrical problems in the motor. Fractional horsepower motors aren't rebuilt, so you would replace it. However, with a 25 year old furnace, you should have the heat exchanger inspected - be foolish to put that time and money into a furnce that needs to be replaced.
--
Scott McDaniel

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dog wrote:

Bad run capacitor or high temperature cutout opening due to overload.
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After checking the replies, I pulled the panel on the furnace to inspect the motor area. Much to my surprise, the filter was more clogged than I had expected. It seems it wasn't that long ago that I changed the filter but I guess it was longer than that. Anyway, I installed a fresh filter, turned on the blower, and it has not cut out since then. So I guess the clogged filter was causing the motor to overheat. But I have been in this house for 10 years and this has never happened to the motor before. I've never exactly been religious about changing the filters but I've always changed them several times a year. I guess this is my wake up call from an aging system--better be more disciplined about changing those filters. The A/C components are even older--somewhere between 25-40 yrs. Just trying to delay the inevitable...
thanks all
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I normally tell my customers to check the filters at least once a month and change them when they become dirty. Mine at home needs changed every month.
Stretch
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A clogged filter will take the load off the fan motor. This is something that many people fail to understand.
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Load is off, RPMs increase, and without airflow, motor overheats.. basic stuff...
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you are dead wrong on any residental type blower motor, a clogged filter will reduce the load on a motor. If you have a overload condition on a blower motor, and no other way to reduce the load, and installing a damper and closing it till motor is not overloaded is done, also the method to unload a circulator pump same thing.
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