Hey, TractX, I'm Greg Fox and today we're going to talk about diagnosing a bad blower motor. I wanted to expand on our recent gas furnace troubleshooting series by going into each part of the sequence of operation. If this is your first time watching our channel please click subscribe down here on the bottom right and if you click that little bell next to it you'll be notified of all of our videos as they come out. This video is all about the commonly used PSC motor. PSC stands for permanent split capacitor. The capacitor is a storage bucket of electrons that helps regulate the voltage going to the motor as it starts up and continues running through the cycle. Today's capacitors typically last five to ten years but as always can run much longer. Now before you start taking wires off the blower motor something I've learned over time is I like to use my work phone to take a picture of the wires that are attached to the control board so I don't forget what taps the original wires were attached to. It makes things much easier for me when deciding which colors to put back on where. So what needs to happen for the blower fan motor to start? Well in air conditioning or cooling mode the thermostat calls for the AC to kick on by connecting 24 volts from the R terminal to the Y terminal but the thermostat also gives 24 volts to the G or fan terminal. The Y terminal being energized kicks on the outdoor unit while simultaneously the G terminal being energized at the thermostat turns on the air handlers blower motor. Now in the heating mode the 24 volts at the R terminal connects only to the W terminal to start the sequence of events that happens for the furnace to start up. It energizes the W terminal but not the G terminal in the heating mode because the control board tells the blower when to turn on. That's usually 30 to 60 seconds after the flame has ignited to start heating the furnace up. The delay in the starting of it is because we don't want cold air coming through our ducts while we wait for the heat exchanger to warm up. Smart huh? Once the low voltage signals have made it to the control board terminals a series of connections wind themselves through the printed circuit board where a switch will energize to send 120 volts or in some cases 240 volts onto the blower motor. Check your wiring diagram to be sure which motor you have. Here are eight things that you can do to diagnose a bad furnace blower motor. Make sure it's getting power to it. If you don't have the proper voltage coming in from the board start by checking voltage at the outlet. Then move on to the transformer making sure high voltage is coming in and 24 volts is going out to the board. If you have power to the board and no power going out to the motor and everything else is operating normally in the furnace sequence of operation you may have a bad control board. You can test this by jumping out 120 volts directly to the blower motor wires. This will let you know if the blower motor really works or not. Make sure the capacitor is attached to it is good. Whether you do it before you jump out the blower motor or what check out the capacitor real quick to see if it meets the manufacturer's specs. If it doesn't replace it and retest. Next make sure that the motor isn't getting too warm to the touch. Some motors just get old and dirty. If the blower motors get too hot they can lock up and stop spinning or still spin but have an open winding inside the motor which isn't allowing the circuit to be complete. Check the amtrols and compare it to the data provided by the furnace sticker. Sometimes you have to use a mirror or actually pull the motor out to check the amp rating of the motor. If you have access to the service fax manual of the furnace the OEM motor specs will be listed in there as well. And those blower motor amps do vary quite a bit. Anywhere from 4 amps to 12 amps depending on the size of the furnace and the type of the motor. If the amtrols are too high either the motor could be going bad causing intermittent operation or the static pressure pushing back on the blower fan wheel is so great it's causing the motor to strain to provide air needed. Next up the motor won't spin. If the rotor that holds the fan blower wheel won't spin or is hard to spin it's a good sign that the blower motor is shot. Once again if the blower is getting proper voltage and the capacitor is good but the blower won't freely spin it may have seized which is not uncommon. Next the motor spins but is making a scraping or a screeching noise. You could have proper voltage to the motor but it has the strong awful screeching noise. Check to make sure that the screw cage isn't rubbing against the side of the blower housing. Send in the wheel inside the blower housing and re-tighten the locking nut to the rotor shaft so it doesn't slide anymore. Next the spine of the blower wheel could be separated from its fins the ones that cut the air and throw it into the ducts. The air pushing back against the cups will cause the metal on metal friction creating the noise. The spine attached to the rotor shaft is spinning much faster than the separated wheel itself. Replace the blower wheel and retest it. Next I've seen blower wheels get so dirty that you need to clean it just to get the air moving again. The cups or scoops are filled with so much dust dirt skin and hair that it really weighs down the wheel and creates a strain of the blower motor. Sometimes when it's bad like this and you should tell your customer before you perform the blower cleaning the clean blower wheel becomes light enough again that the motor birds itself out because all this time it was used to spinning a heavier weight. So you could get everything clean and get it going again and two weeks later get called back out because the blower is not working again because it's spun out. If you cover your bases by communicating properly with the customer your company may not have to buy another blower motor. It just looks shady if you didn't. Something to think about. Well I hope this video has given you some good pointers to use out in the field. Diagnosing a bad blower motor can be one of the more intimidating parts to diagnosing a furnace but if you know what's supposed to turn on in the sequence of operation you can go from there by checking the things listed in this video. 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