Quick question for those of you who’ve wrestled with your own demonic attic fans. Or, more accurately, a quick description and then the question.
Our attic fan, for the past couple of years, has been predictably bi-polar: in the fall or early spring, when the weather is cool, the motor and blades spin. Ahh. Come summer, however, and the higher temperatures, the motor buzzes and the blades don’t spin. Frowny-face.
Tonight I climbed into the attic and finally took a peek at the problem child. Auntie Em turned the fan on and, predictably, the motor buzzed and the blades sat there laughing. Giving the belt a tug, though, seemed to catch the motor and start the blades a-spinnin’.
So, we repeated the process. Again, the same thing happened. I removed the belt, saw a fairly decent crack and blamed it as the culprit. I ran to the auto parts store, found the same belt, came back home and put it into action. Alas, that wasn’t the magic (and cheap) fix I had hoped.
My original assumption was that the belt was cracked and slipping; on the verge of total failure, but straddling the line enough that the cooler weather kept it contracted enough to work. Now, I’m thinking it’s a motor problem.
Anyone else encounter a similar problem before? If so, what did you do to fix it?
Sounds like the starting capacitor in the motor. The capacitor may, or may not, be replaceable. Even if it is, finding a new one is often difficult.
The motor probably has a label with its model number. If you Google the model number and the word capacitor, you may find information on how to replace the capacitor or that it’s not replaceable and the motor must be replaced.
If the motor has a cap, that’s my guess as well. If it’s replaceable, you’ll see it mounted to the side of the motor, usually about the size of two or three AA batteries under a metal cover. If the whole motor is easy to remove, I would take the whole thing down and bring it to a place like Grainger and tell them you need a new cap. IME attic fan motors don’t usually have caps, in which case you can just take the whole motor to a place like Grainger or another electrical or HVAC supply house and get a replacement.
If there’s any model numbers or brand names written on the unit anywhere, make sure to write them down and take them with you. It’s a lot easier then having them guess.
Those are good ideas. Thanks, everyone. I’ll probably just brave the tiny attic opening and sweltering heat and detach the motor. It’s pretty simple set-up: spring-attached to a support bar and held on to a swinging plate by four bolts.
What’s odd now, though, is that after I came down from the attic and put everything away, the fan’s working. Consistently. (That is, it catches every time we switch it on.) Which, of course, it wasn’t doing when I first replaced the belt. I’ll grab the sucker, anyway; I bet it’s probably twenty to thirty years old at this point and might be due to for a replacement.
there are lots of bearings in a belted fan that could bind up with dirt, crud and lack of lubrication. in warmer weather thermal expansion might cause a bearing to bind. a little poking and banging can free things up for a minute or weeks.
lube and clean things. the fan blade (ideally) should move when you blow into it (with it unbelted) or spin freely for a while with a finger flick.
Also, there should be no lateral play. If the blade and shaft move up and down a bit, that’s okay, but if it wobbles, it needs to be replaced.
ETA, if you are going to replace the motor, before even going to the store try to get the blade off. There should be a set screw on the side that you can loosen with an allen wrench and then you can remove the blade. It usually needs to be muscled off. Be careful if you use a hammer, if you mushroom the top of the shaft, you’ll never get the blade off. If it becomes too much work it’s often times easier just to cough up the extra $15 and replace that too.
The motor’s not attached to the blade by anything other than the belt, so removing the motor for either attempted maintenance on my part or taking it into the shop won’t be a problem.
Looks like I’ll be detaching it from its plate, grabbing the motor and doing some research to find out its age, the type of motor and what suggested maintenance is. It may indeed be a model which needs renewed applications of lubrication every few years. I’ve no idea what the previous owners of the house did to maintain it, so it might be worth just getting a new motor so I’ll know its history from day one.
Forgot it wasn’t a direct drive. I’d imagine it has a pulley on it that will need to be removed though. The same cautions apply. Try to avoid using a hammer. If you do, try to find away to support the motor by the pulley and then use a screw driver or punch on the shaft and hit that with the hammer so you don’t mushroom the top, or, as I mentioned above, just plan to replace that part as well.
If there are oil holes (usually with a small plastic cap, you’ll want to pick up some Zoom Spout to oil it with. One or two drops is typically all you need for maintenance, maybe more if it hasn’t been done in years.
The generic diagnosis…
If you give the motor a spin by hand and it starts spinning slowly and gradually comes to speed, then the problem is probably gummed-up bearings. If you give it a spin and it starts right up at full speed, then the problem is almost certainly a bad starter cap or centrifugal switch.
Given the inhospitable location and the unknown maintenance history, my money is on gummed bearings in either the motor or at the fan blade. Easy test for this is to remove the belt and start the motor.
You might take a look at new fans while you’re at it. Ours has been acting up for a while (overheating motor) so we’re doing research. It will cost as much to replace the motor as it will to replace the whole fan with a smaller, more efficient unit.