In spite of being a programmer, I’m not much of a DIY person when it comes to computer hardware. For example, I’ve never built a computer from parts, or performed maintenance more complicated than a RAM or hard drive upgrade.

One thing I’ve been doing that has a DIY air to it, though, is cleaning the dust from the inside of my desktop computer using a can of compressed air – a habit I picked up from one of my first-year university roommates.

The first time I did this, I was very hesitant, afraid that I would break something. It went smoothly, though, and I continued cleaning my computer this way regularly (about once a year) without any trouble.

Until last weekend, that is.

After last weekend’s cleaning, my computer booted up fine, and everything seemed OK, but a short while after booting it up, I stepped away from it to talk on the phone, and returned to find it mysteriously powered off.

Powering it back on led to more strangeness: the computer itself powered on fine, but the monitors were receiving no signal, just as if the computer were off.

I powered it off again, and opened the case back up to inspect the internals, thinking that perhaps the cleaning loosened or dislodged a connector; however, everything seemed to be in order.

Powering it on one more time, the monitors were working again, and everything seemed fine. I was ready to write down the mysterious symptoms as a fluke and move on to other things, but within 20 or so minutes, the computer suddenly powered off again.

This time, though, I was sitting in front of it when it did, and I got a fraction-of-a-second glimpse of a Windows dialog opening up before the power-off. I didn’t get a chance to read what it said, but it made me realize that rather than the power-off being a pure hardware failure, it could be something triggered by the OS for some reason.

So I powered on again (monitors working fine this time), and took a look at the Windows system event log, and indeed, there were “Error” entries whose times matched the sudden shutdowns. Most of the event information was pretty cryptic, but once I realized you can double-click on the event to get more details, there was a descriptive message: “System shutdown due to graphics card overheating”.

That explained why the computer was shutting down after running for a short while, and also why the monitors weren’t engaging that one time I powered it back on (the graphics card must not have had a chance to cool down enough). It also gave me a direction to continue investigating in.

I researched the problem of graphics cards overheating a bit, and found that the problem was commonly caused by a fan malfunctioning, or airflow being obstructed by dust.

So I powered off again, opened up the case, and inspected the fans. I saw two, a case fan, and a CPU fan (and possibly one inside the PSU but that was enclosed so I wasn’t sure); the graphics card didn’t appear to have its own fan. The fans seemed to be in order; to be sure, I powered the computer on with the case open and verified that the fans were spinning fine. Nor did I detect any obstruction to airflow.

Nonetheless, the overheating and subsequent shutdown recurred.

I downloaded a program to monitor the internal temperatures of the computer, and verified that the graphics card did indeed get very hot – while the CPU temperatures remained around 40-45ºC, the graphics card’s temperature would slowly rise over time, reaching close to 110ºC, which seemed to be the point where the shutdown was triggered.

Determined to get to the bottom of the issue, I opened the case again and decided to try to remove the graphics card and inspect it more closely; I never got around to removing it, though, because in the process I discovered the cause of the problem.

It turns out the graphics card did have its own fan: a small one, oriented horizontally, built into the bottom of the platform that held the card. You had to be looking at it from underneath, which I didn’t do before, to see it.

This fan wasn’t spinning, and it was readily apparent why: there were large clumps of dust in it, that were too clumped together to have been disloged by the compressed air. In fact, most likely the compressed air treatment caused additional dust from further above to collect there, pushing the fan over the edge to the point where it couldn’t spin any more.

Cleaning out the dust with some tweezers, the fan started working again, the graphics card stayed cool, and all was well.

This sort of problem and diagnosis is probably very trivial for a lot of tinkerers, but for me it was exploring new ground. I’m glad that I persisted in fixing the problem myself and didn’t resort to bringing my computer in to a repair shop.