What kind of lubricant for an electric motor in a kitchen extractor fan?

October 6, 2019 7:46 PM

We recently had our kitchen extractor fail after a lot of screeching. One fan motor got either burnt out or got stuck; it would not run at all, so we replaced it. Then the other fan motor started making the same noises. We lubed it with some oil we had, but now the lubrication is wearing off and this motor is starting to make screechy noises again. What can we use to lubricate the axle so it stays lubricated? Would we need to clean it first?
posted by kandinski to Home & Garden (6 answers total)

I have tried bike chain lubricant on worn fan motors, but it didn't work for long (I followed advice that bike chain lubricant was designed not to attract dirt and debris). I've also seen advice for sewing machine oil, which will be my next step. I was surprised not to find more authoratative advice on fixing fan motors, seems like a very common problem.
posted by reeddavid at 9:05 PM on October 6, 2019

You’ll want to make sure you’re using a lubricating oil. I find 3-in-1 does the trick.

If you can you want to lubricate the bearings, not the axle.

If there is any sign of rust then yes, use a penetrating oil like WD-40 to clean things up a bit before lubing.
posted by Tell Me No Lies at 9:11 PM on October 6, 2019 [1 favorite]

I would use a grease instead of an oil. An all purpose autimotive grease or white lithium grease might work.
posted by nestor_makhno at 9:19 PM on October 6, 2019 [1 favorite]

If it's at the point of making screechy noises, it's probably borderline being toast (or at least needing the bearings/bushes replaced, which is probably hard/impossible to do - most smaller motors like that aren't made to be repaired).

What has worked for me as a longer-term solution than just plain oil is Nulon engine additive. If you can disassemble it far enough to the the shaft out of the bush at each end, great; clean the bush with solvent, & soak it in a 50-50 mix of 3-in-1 oil & Nulon. If you can't get it apart that much, but can get at the end of the shaft & bearing (e.g. by removing a cap or cover), soak as much neat Nulon as you can into the bearing - typically, I'd stand it pointing up and add a few drops every hour or two until I think it's soaked in & feels OK when rotated by hand.

Normally, that's enough to get a few more months or even a couple of years out of small fan or equipment motors where there's not too much loading on the bearing.
posted by Pinback at 10:50 PM on October 6, 2019 [5 favorites]

A kitchen fan is 95% sure supposed to have sealed bearings and not be serviceable. If you were going to oil it it would get exposed to all the cooking oil floating around and would get gunked up immediately.
posted by Huffy Puffy at 6:36 AM on October 7, 2019 [1 favorite]

Best answer: Hi all. It turns out the motor didn't have ball bearings, but naked steel axes turning on brass-looking housings . I dismantled it, lubricated those two points of contact with teflon bike lube, and reassembled it. The brass housings the axles rotate in are mounted on some kind of gimbal, which may have caused the misalignment. The motor's rotor had signs of friction against the stators, but I decided against lubing those because I didn't want to add a flammable fluid to parts that might get very hot or even sparky.

After reassembling, the motor made occasional grinding noises. After re-mounting the turbine on the motor, it seems like the weight of the plastic assembly helps the rotor stay centered, and the grinding stopped. Fan now makes the right sound.

We're kind of resigned that we'll eventually have to shell for a new motor, but for now everything seems to be working right. Thanks all of you for your answers.
posted by kandinski at 8:31 PM on October 11, 2019