Things that you don’t want to see in your hourly logcheck report are messages like that:

Feb 21 00:08:49 sensord: Sensor alarm: Chip w83781d-i2c-0-2d: fan2: 4299 RPM (min = 5000 RPM, div = 2) [ALARM]
Feb 21 00:09:49 sensord: Sensor alarm: Chip w83781d-i2c-0-2d: fan2: 7584 RPM (min = 5000 RPM, div = 2) [ALARM]
Feb 21 00:10:49 sensord: Sensor alarm: Chip w83781d-i2c-0-2d: fan2: 7417 RPM (min = 5000 RPM, div = 2) [ALARM]
Feb 21 00:25:51 sensord: Sensor alarm: Chip w83781d-i2c-0-2d: fan2: 7848 RPM (min = 5000 RPM, div = 2) [ALARM]

There seems to be a bug in sensors where an alarm condition is not always recorded properly. I guess that the fan speed drops below 5000 rpm, then triggers the alarm but speeds up rather quickly again. Anyhow, either sensors is totally buggy or the fan is broken. The machine is rather old, pentium 2 (350 MHz), so I fear that it is the later.