micky on 2017/01/23 wrote:

Can you damage a case fan by vacuuming the air vents from the outside?

(I have a Dell Optiplex 775 with the original fan. )

It seems more than safe to me, but I happened to read the manual for a
Noctua fan and it says not to use a vacuum cleaner or it may apply
"excessive force to the fan". I find that hard to believe. I've pushed
on the vanes of other 3, 4, and 5" fans and they don't bend at all with
the kind of force vacuum cleaners exert. In fact I think they would be
hard to break. Are Noctua fans more fragile than others?

Fans should not be rotated (except by hand to check for bearing wear)
other than under their own power. Spinning the fan not powered will
generate a reverse magetic field that induces current that it may not be
designed to handle. Use an ear swab (a long stemmed one if needed) to
block the fan from spinning when you suck or pass air through it. Your
computer fan is not a simple transformer but has electronics inside,
like to generate a pulse to let the computer know the RPM of the fan.
The fan also was designed for a maximum RPM simply because they are not
that well balanced. You sucking or blowing air through the fan could
result in it spinning at far greater RPM than designed to handle. You
might get away with driving at slow speed with an out-of-round,
separated ply, or unbalanced tire but what happens when you take it on
the highway?

Many fans have the blade hub simply pressed onto the spindle. There may
be an indent in the spindle into which nubs in the fan will press in but
sometimes it is just friction holding the hub onto the spindle. You
sucking on the hub and blades could pull the hub out and cause it to
whack against its cage, protector grid, or case.

When doing a build, I always salivate on getting Noctua fans but they
are just too pricey.

Never use a non-computer vaccum to clean anything electronic unless you
can guarantee that the vacuum (no part of it) touches the electronics.
The air rushing into the nozzle and hose generate static electricity.
There are computer vacuums but they have a price premium. And, no, I'm
not talking about those cheap 1-battery keyboard dusters the size of a
big Sharpie marker which aren't static protected, anyway. You already
know about taking anti-static precautions when working inside your
computer so why oblivious to using a vacuum there? Yes, you might be
thinking you would only use the vacuum on the outside of the closed case
but static shocks to the case have to go somewhere. While the case is
(well, should be) grounded, high-voltage often tends to go where it
wants instead of where directed. I've seen where a static shock to the
case would power it off. That meant the surge somehow affected the
logic on the mobo to cause it to power off the PSU.

Don't use a household vacuum to clean your computer. Take it outside
(when not raining or snowing) and use compressed air to blow out the
dust. That uses more concentrated pressure than your vacuum can produce
through its large hose and you also have better control. Since crud
often builds up on fan blades (the velocity of the dirty air causes the
crud, especially cigarette smoke and cooking oil), you'll want to use a
cotton swab to wipe the blades. That will also get rid of imbalance due
to the impacted crud. You can try to blow off the fans but canned air
often won't have the pressure needed to blow off the stuck-on crud. You
don't want to use excessive pressure, like from a compressor (which
might be oiled), so just use canned air and ear swabs on the fan blades.
Of course, when you take it outside (or, if you're lucky, under a vent
hood) to blow out the fans, you might as well as blow out the heat sink
on the CPU and GPU, through the PSU (both directions, and remember to
block the fans from spinning), and everywhere else inside. Considering
that users rarely blow the dust, lint, pet hair, and other crud from out
of the computers or they have a particularly dusty or linty environment,
you might need several cans of compressed air. I blow mine out at least
once per year but usually twice (spring and fall). I have lots of
carpet (would prefer hardwood floors), pets, and like the windows open
during the non-winter months, and my old furnace sucks at filtering (I
have to replace the fiberglass filter by disassembling a curved frame
instead of buying pre-made replaceable flat ones).

Where in the instructions for your vacuum cleaner does it say that its
use is appropriate to clean out computers, TVs, or other electronics?
Do you use your lawn mower to trim your hedges?