Many people throw fairly new box fans out well before their time. Like most small appliances, people don't take the time to clean them, even though it will make them last much longer. I guess it is easier to put it out for the trash and spend another $20-$30. Whenever I see the towers of box fans for sale, I always wonder what happened to the ones people bought the year before.
After only one season a fan may be covered in enough gunk to give the illusion that the 'motor' is worn out, when really all that is needed is a good cleaning to keep it running for a lot more hours. I have often picked these up on trash day, and gotten years of use from them. Rarely I may have to replace a knob, but usually they are functioning, but the blade speed is about half of normal.
Step 1: Tools
Just a few tools, though you can use many more for cleaning depending on the gunk level.
All Purpose Cleaner/degreaser
Finger Nail Brush
green kitchen scrubbies
Step 2: Remove Front and Back Grills
These screws are usually very small. put them in your pocket or somewhere SAFE.
Sometimes a few can be missing OR the hole has grown too large to reseat tightly.
Yes, you can skip a few, usually you can leave off a side screw without TOO much noise factor.
but you NEED the top and bottom tightly screwed down of the vibration will make a hell of a racket.
scout around for replacements - you want short and fat threads.
Step 3: Remove Grill and Fit
You may have to unhook the power cord collar and remove the feet.
if the feet are missing you will have to dummy a replacement, or just make sure the fan is propped up, like in a window. Vibration at high speeds will make the fan walk and possibly fall.
Step 4: Brush the Motor
Remove all the material surrounding the motor, avoid spraying it with any cleaners.
Use a brush to remove the hair and gunk.
also wipe the struts.
Step 5: Wash Blades
Wash each blade individually on one side then flip the fan and wash the other.
I find that some blades resist degunking and a scrubbie pad is useful to remove the stuck on gunk.
If you leave it gunked and only remove the visual material, new stuff will quickly latch on and you will be just as bad off. You want to end up with smooth clean plastic blades, where things slide off.
Step 6: Clean Fan Grills
This is tedious and you will feel like cutting corners. If you have more than one fan to do, leave the 2nd until the next day. Use a brush for the solid matter. then spray with a degreaser/cleaner and then scrub with a nail brush or other firm bristle brush. Then wipe with paper towels.
The grids are NOT straight but beveled, and may appear clean if you look at them straight on, look at them from an angle and you will see they have four sides, you don't need it spotless, but get the area in front of the blades reasonable clean. You CAN do these in the shower, and use a long handled scrub brush, but you will still need to use paper towels to get in some crevasses.
Step 7: Reassemble the Fan.
Wipe the whole thing down inside and out.
Reattach the grills, the feet and align the power cord collar.
Turn it on, if the fan was not old to begin with you will find a world of difference between the speed of the fan blades before and after the cleaning.
I do this every season to my own fans and these $20 box fans last a lot longer then the manufacturers want them too.