______________________________________________________________________ The A/C blower motor in the attick won’t run and the unit hums very loudly. What’s making the hum noise? The hum cycles; staying on for about 30 seconds and then off for 30 seconds. The hum goes away when I turn off the power. When I discovered the blower motor wasn’t running, I also found that the outside compressor was running continuously; and one of the lines coming into it had 1/2 inch of ice around it when it was 95F outside. I turned off the power and let all the ice melt. Does the ice mean I have a problem with my line? When I turned the power back on, I verified that 115VAC is coming into the furnace transformer and 24VAC is coming out of the transformer. There is a status light of some kind on the Furnace Integrated Controller board, but that light is always off. Does this mean the Integrated Controller board is ok? I tried rotating the blower fan blades manually to see if they would continue on their own. The blades would not continue on their own. Does this mean that my blower motor is bad? The Gas Furnace I have is Model number G8C10020MUD11A. I’m guessing this furnace is about 7 years old. Thanks in advance for your help! I’m confident you guys have some answers for me. Cheers Ted Replies: diaz “Re(1):A/C blower motor won’t run and loud hum” , posted Sun 8 Jul 09:28 ______________________________________________________________________ It sounds like the motor is going into thermal overload. If motor never run at all, starts to get very hot-hums, then stops and starts humming. Motor and Capacitor may be bad. The reason I say may be is because: 1.Replacing the capacitor,checking connections at the capacitor could also be the fault. 2.Control board could be bad also. Why? Board is running motor in two speeds at the same time…hence causing motor not to run and causing damage to it. These are issues that should be looked at by a TECH. WARNING! Capacitors can hold a dangerous charge, so if you have any lack of electrical know how, pass it over to a pro. you could be killed… As far as icing up is concerned, it iced up because blower is not running. Control Board has an indicator LED which indacates if power is applyed to it, and may display falt codes. Your door pannel should give you data code reading. prior to condeming Control Board, bench check motor first. AGAIN. WARNING.. HIGH VOLTAGE CAN KILL, IF YOU DONT HAVE THE SKILL. Not knowing all the answers is human. knowing how to find the right answer is an ART
tcf “Re(2):A/C blower motor won’t run and loud hum” , posted Sun 8 Jul 13:49 ______________________________________________________________________ Thanks for the feedback. I knew you guys would be helpful. The Status LED on the Control board is in the “Steady Off” state. According to the legend on the side panel, the “Steady Off” state means “Normal Operation.” Is there another way I can verify the Control board is ok or should I assume it’s ok for now? What is the approximate cost of the Control board? Thanks for the WARNING! I do have some electrical knowledge and am well aware of the discharge capabilities of a capacitor, etc. My meter doesn’t test caps. How do I test a capacitor? What is the approximate cost of this capacitor? Thanks for the WARNING! I definitely won’t try spinning the motor again. The power was on when I tried spinning it manually, but it didn’t help the blower motor to start running. The Blower motor doesn’t run at all. How do I bench check the blower motor? What is the approximate cost of the blower motor? Thanks again for all your help!
Cheers Ted diaz “Re(3):A/C blower motor won’t run and loud hum” , posted Sun 8 Jul 15:00: ______________________________________________________________________ Never “assume” anything-ever!. Verify 1st to see if you have a bad mortor,cap, board or just a lose wire etc.. If you replace just the motor, and the board is bad, you lost another motor. or if you replace the motor and still will not work, you have two working motors on your hands, and have less money in your pocket Control boards can run $60 to $1000s of $$$$, it all depends on your model. Ask your supply house for pricing, even for the motor. They may even help in bench testing motor for you. If you want to do it your self, check motor for open circuit between hot and common. See if you are getting proper voltage to motor from control board. check to see if door safty switch is good, is it closing the circuit?. A new capacitor is about 10-30 bucks. Motors? $75-$200 and UP, all depends on voltage,# of speed, rpm, frame type,HP,# phase. ect..ect..ect A capacitor tester is about 100 150 There are some of the steps in the diagnostic process you have to do befor you buy any parts. If you have a local HVAC or Motor company call them and ask if they would “bench test motor” for you. HOPE THIS HELPS Not knowing all the answers is human. knowing how to find the right answer is an ART
[this message was edited by diaz on Sun 8 Jul 15:05] Banger “Re(1):A/C blower motor won’t run and loud hum” , posted Sun 8 Jul 09:01 ______________________________________________________________________ The loud hum is probably the motor trying to run. Most likely the motor or the run capacitor is bad. The motor has a thermal protector built in so that would be why the hum cycles on and off. If you tried to spin the motor by hand with the power off, or while the motor was off on it’s thermal protector then it wouldn’t stay running anyways. DO NOT TRY TO SPIN THE MOTOR WITH THE POWER ON. I HAD TO GET 37 STITCHES IN MY HAND ONCE FROM A BLOWER WHEEL. The ice is a result of the motor not running. No air is blowing across the evaporator (indoor) coil so the condensation freezes on the coil and lines. The light on the board may or may not indicate a problem. Some only blink if there is a problem, some light up or blink to show power to the board. It depends on the board. Shut everything off and let it cool down. Have someone test the motor capacitor and replace it if it’s bad. If not then you probably need a new motor.