wlr211

I have a very old gas, forced air, Luxaire furnace model #GH102SE and am trying to limp through one more winter season.

The blower motor can not turn the squirrel-cage fan. I can manually move the fan belt and the fan easily turns. But when the motor receives the signal to start, it jerks the fan belt and fan into action but immediately everything stops and the motor makes a buzzing sound. I've tried to manually move the fan belt when the motor is making the buzzing sound and it feels like the system is frozen.

The motor is about 10 years old and I replaced the fan's axle and bearings last season, beginning of 2009. I also replace the original thermostat with a Honeywell digital thermostat last year. The pilot light seems to be functioning properly and the burners ignite and stay lit.

From my description does it sound like the motor is bad? Should I disconnect the fan belt and see if the motor can turn? If it does what would that mean?

Any help would, of course, be appreciated.

Bud Cline

Is this motor a "capacitor start" motor?
Does the motor have a small dome-like cover perched on top of the motor housing?
More than likely it's a bad capacitor.

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wlr211

Wow Bud, thank you for the very quick reply. I really don't know enough to know if it is a "capacitor start" motor or not. I don't think there's a dome-like cover on top of the motor but I'm going back down to the crawl space to have a look right now.

I've been reading about capacitors and it would seem that, if I have one, that might be my problem given the fact the motor isn't really all that old. I'll report back when I have more information.

Bud Cline

I'm not an expert and I don't know that much about electric motors either but I did major in that type of thing in high school many decades ago. A lot has changed since then I'm sure but if my memory serves me correctly (and it doesn't do that so much anymore) I'm feeling a capacitor issue here. If the motor does not have a capacitor then we have already exhausted my knowledge of the subject.

My recall is that capacitors are used to start a heavily loaded motor and get it to a certain rpm at which time the capacitor leaves the circuit and the motor runs on its own with less need for the added assistance. It takes more juice to start an electric motor than it does to run one. Once the initial start-up load/drag has been overcome the capacitor is no longer required.

Doesn't sound to me like the motor is able to reach the "run" stage.

Hopefully someone here will come along with more knowledge than I have about such things.

In high school I built an electric motor from the ground up. I personally hand wound the windings and all that stuff and the damned thing actually worked. To this day I remain impressed with my ability in that field. But, that's as far as it goes. You now know what I know.

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Wuzzat?

How old?
25 years +/- 3 years is avg. for "resi. HVAC equip."

A buzzing sound may mean a bad connection. See what the motor voltage reads during the buzzing.

Does your motor look like this?
http://www.hvacrheritagecentre.ca/exhibits/collections/images/artif_283.jpg

Bud Cline

Strummin' my fingers on my desk top waiting for this cliff-hanger to end!!!!

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wlr211

Bud, this cliff hanger is hardly worth waiting for but here's what I'm guessing.

I looked at the motor and didn't see anything I would describe as a capacitor attached on it or even nearby. I disconnected the fan belt and turned on the motor. It did not work but, rather, made the buzzing sound.

I turned off the power and manually rotated the motor pulley. It turned but was making a "crunching" sound. I then noticed that there was a very slight amount of play in the pulley. It moved in and out of the motor housing. And I also noted that I could make the pulley lock-up by pressing inward on it. As I said, the play was very slight, maybe 1/4 to 1/2 inch at the most but it would lock up.

There is an electrical junction box on the outside of the furnace assembly that the two wire leads from the motor go into and other wires are attached to the outside. I guess these come from the thermostat. I doubt there's a capacitor inside this box but could be.

I'm thinking I need to remove that motor, cut it's wires and replace it.

By the way, the schematic glued to the inside of the cover door of the furnace shows a capacitor beside the motor but it say "if used" underneath it. I'm guessing not all motors for this model furnace used a capacitor.

I'm also guessing you can stop strumming your fingers now. Thanks.

wlr211

Wuzzat...just noticed your reply and yes I know I'm on borrowed time with this furnace. Thanks for posting the picture but, no, my motor does not look like that one. There is not a dome on top of the motor housing and my motor appears to be a little longer and not to have quite as big a circumference as the one you pictured. Thanks for responding to my plea for help.

Bud Cline

OK one last guess.....and it is only a guess.

If that motor is old enough to have "brushes" that could be another possibility. Once the brushes wear down they become small/short enough to leave their individual housings/retainers and can temporarily lock an armature and keep it from turning. The motor's commutator windings would still hum when juice was applied but the brushes wouldn't be able to deliver juice to the armature and would be in disarray inside the motor.

There was a time when motors had access to the brushes by removing a small threaded plug on either side of the housing. Inside and under that plug is/was basically a piece of carbon and a spring and wire lead. You could pluck the brushes (carbon remnants) and replace them easily enough.

OK, Now that's all I got for sure this time.

Just trying to save buying a whole new motor is possible.

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wlr211

Thanks, changing brushes out may be a stretch for a man of my limited abilities but I'll take a quick look. Guess I'll also make a few calls and see what kind of dollars I'm talking about for a new motor.

Thanks again to you and Wazzat for weighing in. As with Tennessee William's Blanche DuBois, "I've always depended on the kindness of strangers."