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Hi, I have a Carrier Weathermaker SX that is probably 30 years old. It has worked tirelessly and has not needed service for many years. I returned home the other day and it was in a shutoff loop because the blower is not functioning. It lights up (the gas flame) and just overheats. The blower hums/buzzes. I am able to turn the squirrel cage but I don't feel like it is turning as freely as it should.

I would love to confirm that it's just the blower and fix it myself. But what else should I check and do I need to consider a new unit on principle because of it's age?

As an aside, a buddy of mine had older furnace replaced recently and it simply does not blow as hot as his old one. It takes much longer to heat the house from a cold state and runs much more frequently than the old one. Is this typical of newer vs. older units?

Thanks in advance!
 

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no way we can tell for sure but if capacitor good and motor has power its safe to assume you need to replace it... as far as the new furnace not blowing as hot that may well be true.... its probably ..... way less input than the old one and way more efficient.... the furnace must be set up for a proper t.d. ..... contractor that installed it should of hopefully set the new furnace up......:eek::eek::eek::eek:
 

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Blower motor

Sounds like the blower motor bearings are gone. When they wear the motor struggles to start smoothly and it may overheat and take out the motor windings/related components. I would replace the motor and capacitor on the unit. The unit is overheating because as it heats in the heat exchanger the heat is not removed because no airflow is going across the outside of the heat exchanger to blow into the ductwork. So it may trip the hi-limit temperature switch which cuts power to the gas valve. As far as your friend noticing change in new unit compared to old. Hard to say as it can be many variables. Undersized unit installed, new thermostat now reading differently/not adjusted right if older style.
 

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Buying a motor

Not sure if you have replaced motors before. Frame number on the motor tells all. Shaft size, mounting dimensions etc. if you find one just confirm normal rotation. Mark your wires, cell phone image is good to have as well in case you need to show parts person application. Most units were designed to be unwired and slide out blower assy and all. Once out notice you blower fan to wall clearances and jot down. Remove set screws ( some squirrel cages have a notch on the blade that lets you use the long part of the allen wrench) once out spray into hole with some kind of rust buster if needed and go get a cup of coffee , let the liquid do its thing. If you pull wires from capacitor do so with insulated pliers. Once out discharge it to be safe. If motor shaft is longer , you can always cut excess. Place excess part of shaft on vise and cut with hacksaw to length, hang on to motor! You dont want shaft bouncing around as you cut, keep in mind it has to stay true. Before you install it notice if the new motor has oiling holes , if it does keep the orientation up so you can lube it later on. If the motor has two or three speeds normally the low speed is used for heat as very little air is needed to move warm air. Match the speed of the old and cap off each of the other wires not used independently. Good luck, take your time do well. Joe
 

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I would check the bearings and if they are binding replace them and the start cap for the fun of it. Clean out the buckets of the wheel and see if she dosent kick right off. Use super lube on the bearings. That furnace does not owe you anything, true, but from what I have been reading here the new ones cant shine the shoes of the old models.

I have a 20 year old carrier, and I just replaced the main board, igniter and pressure switch for 170 bucks. Cleaned and lubed motor and she runs beautifully.

She failed because I just moved into the house and the PO did nothing in the way of PM. The Guy was a Plier Mechanic.

The new furnaces are more efficient, true, but how efficient is it when one service call is equal to three months of energy bills?
 
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