Back in my field tech days, I worked for a systems integrator/consultant that dealt primarily with schools and small businesses. One day, we got a call from the school secretary at one of our clients. Her monitor had apparently died, so I scheduled her for an appointment the next morning and drove out there to take a look (it was about a 35-minute ride from our office.)
Upon my arrival, she greeted me and told me that her monitor had been working fine all morning. Being the diligent tech that I was, I still spent some time and checked every pertinent thing I could think of – Windows power save settings, loose power cord, etc. I couldn’t find anything amiss, so I told her to keep an eye on it and let us know if it happened again.
Sure enough, the next day, she called and said the monitor had shut down again. I took the 35-minute ride, walked in the door, and was promptly greeted with “It’s working now!” I took another look at everything, this time even taking the case off the monitor to check voltages, etc. (this was before the days of LCDs, so we’re talking old-school CRT monitor.) Still, nothing seemed out of place.
Then it hit me: what had changed? I suspected there was some other factor that I was missing. Maybe the secretary was messing with cables, poking around at the back of the monitor, etc. So I asked her to call me if it happened again the next day, expecting that it definitely would, and this time she was to just get up and step away from her desk the moment it shut down.
The next morning, I packed a spare monitor in my car just in case, and went out for my morning service calls. Sure enough, the call came, so I drove out to the school.
This time when I walked into the secretary’s office, I immediately noticed a stack of folders sitting on top of her monitor. “AHA!”, I thought. Upon inspection, the monitor was a little warmer than it should have been. I removed the stack of folders, waited about 15 minutes, and the monitor came back to life. The blockage of the ventilation slots was causing the monitor to overheat, and hence, shut down!
I asked the secretary about the folders, and the mystery unraveled further: she had just started putting them on top of the monitor the day of the first shutdown. When I scheduled her for the initial service call the following morning, she had removed the folders and everything else from the surrounding area so I could work (how nice!) Of course, in the intervening time, the monitor cooled off and started working again. After I had gone, she put them back. Same deal the next day.
After we both stopped laughing, I told her I was only going to bill her for the first service call, since even though I considered myself a very capable technician, I was obviously a terrible detective.
The moral of the story: go beyond the obvious when troubleshooting what seems to be a technical issue. Sometimes the root cause of a problem is not apparent at first blush, and you have to put on your Sherlock Holmes hat to figure it out!