Phantom fan? [FIXED - DUST ON HEAT SINK]

[TheLastMan]

My X61s has suddenly stopped making any fan noise at all and there is no obvious air movement around the heatsink. At the same time it has started randomly crashing. The symptom is it will suddenly lose power and shut off with no warning.

I installed Thinkpad fan monitoring software and it shows the fan as rotating at between 3000 and 5000rpm. Is there any way the fan blade assembly could have come adrift from the motor spindle so the motor is still rotating (and being picked up by the sensor) even though the fan itself is not shifting any air?

The temperature is now normally around 70 - 80c. This does not obviously rise before it crashes. I have no idea what it was before the fan appeared to stop working.

[Brian10161]

You might want to install HWmonitor and check the temperatures there.

Only other thing I can figure, is you might have the open up the computer and see if the fan is spinning or is at least freely moving. I don't know if yours will allow it, but if you remove the keyboard, you should be able to access the fan.

Good luck!

[TheLastMan]

I have installed TPFanControl, and this shows the fan spinning at 3,000 - 5,000 rpm. But as I said above there is no evidence of any air being moved. The fan used to make quite a noise when it kicked in and there was a noticeable breeze from the heat sink vent. Not any longer.

The fan on the X61s is underneath the motherboard, so taking off the keyboard will not show anything. The fan input vent is underneath the laptop and is covered by a plastic cowling which is part of the battery - presumably to stop stuff getting in. I may try running the laptop without the battery but with the charger plugged in and see if I can see it spinning.

The temps do not seem to be getting high enough to cause the processor to shut down (that should occur at around 95c), but if there is no air movement in the case it could be that other components are getting too hot (memory?) and causing the shutdown.

This is a company laptop so I cannot start taking it apart, however the company are replacing them all soon so I just want to keep it going until the replacement arrives. Otherwise I will be given an old laptop left behind by somebody who has left the company and I will lose all my installed applications.

I have bought a cheap and nasty StarTech USB powered external fan that clips on to the outside of the vent and draws air out. It is a bit of a bodge but I am hoping it will avoid me calling on the services of our IT department! Their policy seems to be if it is broken and out of guarantee, throw it away and give the employee something older and even more likely to break!

[edit]The other giveaway is that you can use TPFanControl to control the CPU fan (strangely!) and stopping the fan completely or running it at 5,000 rpm makes absolutely no difference to the temperatures![/edit]

[Brian10161]

I'm pretty confident you answered your own question then.

[TheLastMan]

I'm pretty confident you answered your own question then.

It seems like it. I just needed to share...

It does seem rather an odd fault to give a phantom reading on a stationary fan. Do you know how the ACPI interface actually measures the rotational speed of the fan?

[TheLastMan]

Removed battery so fan input grille visible, plugged in PSU and started up laptop. From the view through the grille it was clear that the fan was spinning, not a phantom at all!

However cooling still rubbish and no air coming out of vent. Borrowed a can of compressed air from IT department and blew air through input grille and great fluff balls flew out of the heatsink vent!

CPU temp has now dropped from 70c to 52c and responds well to changing fan speed.

Should have looked at the obvious solution first

Mind you, in the process have found this brilliant app - TPFanControl. Cannot recommend it more highly to those with ThinkPad fan and cooling issues.

[Brian10161]

There's a hall effect sensor on the PCB in the fan that senses the speed. I have seen them on residential furnace blower/induced draft motors and they read quite accurately. Just sends out a signal every time the hub rotates and the motherboard interprets it.

They can be troublesome sometimes, but for the most part they work quite well.

Glad to hear you got it all sorted, dust can be such a bother

[TheLastMan]

...dust can be such a bother

This morning I applied the nozzle of a Dyson vacuum cleaner to the heatsink vent for a couple of minutes.

After removing the Dyson the heatsink was visibly cleaner. The idle temperature has now dropped even further from 52c to 45c and running a "stress test" using 100% of the processor I cannot get it to rise above 51c. I have set the fan to kick in at 45c.

When I first started this thread the idle temperature was 70c and it would quicly rise to over 80c if put under load.

Clearly a bit of dust is enough to cause a rise in idle temperature of 25c!!
This incident has taught me a lot. Thanks for the explanation of the fan sensor.

Have a good weekend.

[Brian10161]

Those temperatures sound pretty good for such a small laptop. My T60 is only slightly lower at idle, sitting around 41'C.

Take care mate, and have a good one too!