Help with bathroom fan that is driving me bonkers
November 14, 2014 1:16 PM   Subscribe

The fan in one of our bathrooms has been working intermittently since I cleaned it (more inside)--most recently, it worked for a few weeks, but is having trouble again. It will start if I "jump start" it by starting it spinning, and then seems to run fine. Not sure what to do, but due to the fan's slightly odd size, I don't want to replace it (i.e., cut up my ceiling) if possible.

I took down the identical ventilation fans in our first and second floor bathrooms. Both were absolutely caked with probably 10 years' worth of lint and fluff and who knows what. Each fan--an older model made by Panasonic--was easy to remove. It was just a jumper for power and three screws. After a vigorous cleaning, I reinstalled each. The second floor fan has had no problems.

Salient detail: the fan that is struggling now fell on the floor at one point. There was no visible damage.

When I first reinstalled the fan, it worked fine--then later that day, my wife reported that it made a noise, and stopped blowing. I've since taken it down, taken the blower out of the plastic housing, loosened and tightened the blower drum (it's got a drum, not fan blades), and put it back up. Presto, works again--until it stops.

The fan sounds normal when its running. When it's not running, you can hear the motor struggle. Again, if it's stopped and struggling, and I kick start the fan by spinning the drum, it works. I don't hear bearings grinding or anything like that, and the motor spins smoothly. There are no mechanical obstructions.

A replacement motor is available, and I really can't imagine what could possibly be wrong with this other than the motor. But given that it works happily for a couple of weeks at a time, doesn't grind, and will work when I spin it make me puzzled. I guess capacitor problems? I'm not sure why that would cause only intermittent issues.

posted by Admiral Haddock to Home & Garden (8 answers total) 1 user marked this as a favorite
You could oil it and that may help, but you'll probably have to replace it. Eventually it will burn out completely (sooner if you don't oil it.)
posted by Obscure Reference at 1:22 PM on November 14, 2014

The stopping and starting, and the need to kick-start the fan, suggests that the motor brushes are very worn.

Sometimes it's possible to obtain replacement brushes or generic ones of the right size, but it's not always possible to get to the brushes. Most people would resign themselves to getting a new fan.
posted by pipeski at 1:47 PM on November 14, 2014

A dead start capacitor will keep an AC induction fan from starting, but will allow it to run if you get it spinning. Can you also start it backwards?
posted by Huffy Puffy at 2:07 PM on November 14, 2014

The bathroom fans I'm familiar with are primitive creatures w/o capacitors (or brushes).

Despite the fact that you dropped it (which could cause a bent shaft or displacement of the structures the shaft passes through) this sounds like a lubrication problem, and I notice you don't mention reoiling the motors.

My fan motors have structures that hold the shaft bolted to either side of the laminated iron frame of the motor, and each of these structures has a very unobtrusive hole in it leading to absorbent packing which feeds oil to the bearing.

If yours is like that, get a light oil in a needle applicator (such as sewing machine oil -- not WD-40) and squirt a moderate quantity into those holes, let the fan sit with the holes pointing up for an hour or so, put it back in and see how that works.
posted by jamjam at 2:46 PM on November 14, 2014 [1 favorite]

If a replacement motor is available, it should say whether or not it's a sealed-bearing motor. If it is, you shouldn't lubricate it. I would also expect it to make noise if it needed to be lubricated.

If you replace the capacitor, make sure you get one rated for at least as high AC voltage, and as close to the same microfarad rating as before. You don't want it to "outgas" ('splode) again.
posted by Huffy Puffy at 3:48 PM on November 14, 2014

3 in 1 Oil works like a charm in fans.
posted by Splunge at 4:17 PM on November 14, 2014

Ventilation fans are crap. What you describe is perfectly consistent with a lack of lubrication and presence of contamination in the bearings. It is most likely not possible to re-oil the bearings as they aren't provided with fittings, and the dirt has probably worn down the bearing surfaces anyway. You can sometimes get an improvement with a thin oil like 3-in-1, which is the only kind you can get into bearings not designed for oiling, but that kind of oil won't last long in this kind of service and it won't fill the gap between the bearing surfaces properly like thicker oil would. Bottom line is you might get a few more hours of running out of it but you might as well save the hassle of taking it down and putting it up four or five times and replace it now.
posted by localroger at 5:31 PM on November 14, 2014

Response by poster: Update: I replaced the motor, and it seems to be working fine. I was getting some funny readings from the capacitor, too, and if I have to, I can replace that easily (it took a really long time for a motor to become available).
posted by Admiral Haddock at 5:58 AM on December 23, 2014

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