I have an HP a6400f PC, (it's a tower) and after a brief power blackout, I started getting a generic "Fan error" problem upon startup. I can click through the error and boot into Ubuntu. Bios/diagnostic tools show nothing unusual.
I opened the case and checked the fans and cleaned them with compressed air. (They were a kind of mess btw). What I can tell from inspection is that CPU fan, case fan and power supply fan are all running. The CPU fan is running pretty intensely so I'm guessing that's not the problem.
I'm on Ubuntu, and the output of the sensors command brings this (when the case is opened)
radeon-pci-0400
Adapter: PCI adapter
temp1: +68.0°C
coretemp-isa-0000
Adapter: ISA adapter
Core 0: +51.0°C (high = +86.0°C, crit = +100.0°C)
Core 1: +51.0°C (high = +86.0°C, crit = +100.0°C)
f8000-isa-0a00
Adapter: ISA adapter
+3.3V: +3.33 V
3VSB: +3.36 V
Vbat: +3.28 V
fan1: 2555 RPM
fan2: 1006 RPM
fan3: 0 RPM ALARM
fan4: 0 RPM
temp1: +44.0°C (high = +70.0°C, hyst = +60.0°C)
temp2: FAULT (high = +100.0°C, hyst = +85.0°C)
temp3: +28.0°C (high = +100.0°C, hyst = +85.0°C)
[Update: Readings after I close the case seem slightly higher, but basically the same] I can definitely see and hear that both the PSU fan and computer fan are running. However, the computer fan seems to be running slow, and I can barely feel any circulation going out from it. Honestly, though I have no idea whether this is how it's supposed to be.
In the sensors output, I have no idea what f8000-isa-0a00 refers to. Also the PC seems to running like normal (I've had it running for only an hour).
This sounds like a sensor problem rather than a fan problem, but I confess I don't know a lot about what is considered normal in the cooling department. Any ideas or suggestions? Thanks.
Update: My problem has been solved by Michael Kjörling, which was reseating the connections. However, I still welcome info and advice about how to make sense of the readings and how to decide whether a running fan nonetheless requires action/replacement.
f8000-isa-0a00is the motherboard sensor bus. You also list three fans, butfan3showsALARMand 0 rpm; I'd say something is amiss, but it might not necessarily be a cooling problem (think sensor problem). It'd be easier if we knew anything about what the sensor output looked like before you started having these issues, to have a baseline for comparison.