Fixing a box fan?

[omgwtfbyobbq]

I have a little box fan here that just stopped working. Every now and then, this will happen and I can open 'em up and clean 'em out to get everything going again, but sometimes, it just won't go. The motor turns well w/o resistance, and the switch seems to be switching, so the only part I could see going bad is a little box with a mF, V, and temp rating. I'm guessing there was too much dust and it got too hot. Does anyone have any idea if I'm on the right track, and if so, where I could get this part or something similar for a decent price?

btw- having operators and whatnot for smilies is awesome!! :gtoet:

 

[Optikon]

I have a little box fan here that just stopped working. Every now and then, this will happen and I can open 'em up and clean 'em out to get everything going again, but sometimes, it just won't go. The motor turns well w/o resistance, and the switch seems to be switching, so the only part I could see going bad is a little box with a mF, V, and temp rating. I'm guessing there was too much dust and it got too hot. Does anyone have any idea if I'm on the right track, and if so, where I could get this part or something similar for a decent price?

btw- having operators and whatnot for smilies is awesome!! :gtoet:

Post a pic of the parts so we can determine what you are talking about (presumably a capacitor?)

 

[omgwtfbyobbq]

Here it is.
**broken link removed**

 

[HarveyH42]

The start cap looks healthy in the picture, not swollen or cracked. I'd grab my meter and start checking the simple/quick/cheap stuff first. Check the switch, they can get a carbon build up on the contacts over time. If it's some thing you plug in the wall and move around, check the cord with the meter, move and bend it some. Should see some change if there is a break in the wire, analog meters are best for this. Motors are tough to kill, but usually stay dead (internal fuse).

 

[TheVictim]

Those AC induction motors do NOT have a lot of torque, it is likely dust in the bearings/lubricant. Something that will save your box fan (and your lungs) is to duct tape a HEPA furnace filter on the back of the fan. This will filter the air AND save your bearings. You also don't have to clean the blade this way.

 

[omgwtfbyobbq]

I checked out the bearings and they seem to be o.k. Which checks out, because it spins just as well as my other fans, and if the bearings are dying, I can usually slap it after I plug it in to get it going. I removed the power wire and a wire associated with one of the speeds, connected 'em and got nothing, so I don't think it's the switch. The only thing I can't check reliably is the wire, since I'm guessing my $5 digital multimeter won't show enough of a difference when I wiggle the wires. Is the internal fuse this little zip tied packet market "F"?
**broken link removed**

 

[things]

omg is that the motor?.....that's scary

 

[G8RPI]

Box Fan

Hi,
From the photo of the motor it is clear that the windings have overheated, the mealted cable ty is a dead giveaway. The motor is basically trash, they are not worth re-winding. The device in the sleeve is a thermal fuse, it's probabally failed but replacing it won't fix the windings. Even if you replaced the fuse and it ran for a while it would not be safe and reliable.

Robert.

 

[omgwtfbyobbq]

Huh, that's interesting Robert, what's the cable ty? From what I can see, everything seems to be intact, but has a pretty think layer of dirt/junk on some parts. Would that look like a melted something or other?

 

[TheVictim]

What he trying to say is brown and bubbly is NOT the usual condition of a cable tie. It's fried.

 

[omgwtfbyobbq]

Ah, so the cable tie being fried implies the motor is fried? Damn... I was hoping to fix it too. Oh well. Thanks for all the help everyone!

 

[Hero999]

omg is that the motor?.....that's scary

It's a single phase induction motor; there's nothing unusual about it. From you're reaction, I take it you haven't seen one before.

 

[omgwtfbyobbq]

Wait, so is the motor o.k. or toasted? Would more pics help?

 

[things]

It's a single phase induction motor; there's nothing unusual about it. From you're reaction, I take it you haven't seen one before.

i was meaning how it was all melted and brown

 

[omgwtfbyobbq]

The copper windings aren't melted at all, the brown you're noticing was just dust/cobwebs that had accumulated and stuck to some sort of grease after I sprayed it off earlier. The lines wrapped around the copper look sort of fuzzy, but isn't that just some sort of insulation?

 

[Andy1845c]

Is the second zip tie from the right melted? Or is it just an illusion? Does it smell burnt?

 

[omgwtfbyobbq]

All the zip ties were discolored on the inside of the copper coils, kinda the same color as the plastic wrapping around the wires. There's this fuzzy cord wrapped around the windings, and the occasional smudge of dusty grease, but nothing looks melted. I'm guessing the thermal fuse is in one of those lines connected to the cap. It smells, metallic, if that makes any sense?
**broken link removed**

 

[sage]

i have a box fan that the stress relief device is coming off the bottom of its frame and i can not find anything on how to reattach it properly to the frame please help! i do not care if i have to self tap the steel rod and screw it back together but i really need some advice please and thank you . also happy forth of July everyone and thanks for reading my post

 

[dr pepper]

If you mean the cable stress releif just tie wrap or insul tape the cable to something solid, unless you can see bare wires should be ok.

 

[MrAl]

Hi,


I've seen these things burn out a million times now. I used to have a nice fan a long time ago that worked so well that i did not want to loose it, so every time it got 'slow' i took it apart, cleaned it, oiled it, and it worked again for another few months. Motor oil seemed to work the best out of everything i tried.

But in the more modern fans they install thermal fuses. These look like little black squares with two wires coming out of them. If the motor freezes up the coil gets hot and it blows the thermal fuse and all the power to the fan motor shuts off. The only way to fix this is to take it apart and replace the thermal fuse with a part that is the same as the old part. Usually the rating is 2 to 3 amps, but it could vary a lot with the size of the fan and manufacturer.
You can tell if the fuse is blown because the fan will not even attempt to turn or make any noise. If you 'fling' the blades with your hand, still nothing (sometimes that starts them when they are sticking). But if the fan makes a noise like it is trying to start then it isnt the fuse.

Another problem that comes up is the core to core alignment. The core has a top piece and bottom piece and larger midsection. To get the armature out you have to take off either the top or bottom piece or both, and when you put them back together again (after cleaning and oiling) sometimes they may not fit exactly together again so you have to jiggle them around a little then tighten the screws a little and try it, then jiggle again and try it, etc., until finally the alignment is right. This doesnt happen with all fans, but with some fans it does.

Another problem that comes up is that the inside of the bearings are really dirty. The only way to clean this is to get something inside the bearing that rubs on all the inside surfaces. I used a dowel that was almost the same diameter as the inside of the bearing, just a little larger, and forced it into the bearing while turning it back and forth to clean out the built up carbon on the inside bearing surfaces. Once done, it usually made quite a difference on the running of the fan.

It's also a good idea to check the speed of the fan periodically. When it is cleaned it runs fast. You can check it by directing a laser pointer through the fan blades as they are turning, and on the other side have either a solar cell or a cadmium sulfide cell with small battery and resistor. As the fan blades rotate they break the laser beam periodically so you can measure the output of the solar cell (or photo cell with battery and resistor) with a frequency counter. You can then compare readings over time to see how the fan is doing after it runs for a few weeks.
The actual frequency measured will be higher than the actual rotation speed. To get the rotations per second you divide the measured frequency by the number of fan blades. But you dont have to do this if you dont want to, as long as the frequencies measured are close to the same each time you check it.
You can check your computer fans this way too.