Stopping the 'fan always on' problem once and for all!

[K. Eng]

The 'fan always on' problem has plagued some T4x models as far as I can remember. My own T4x seems to have had this problem for some time. My theory is that the WiFi card is generating a lot of heat and constantly tripping a thermal sensor that the embedded controller polls.

A description of the problem can be found at:

http://www.thinkwiki.org/Problem_with_fan_noise

The Fan is always on, even though the processor is rather cool.

IBM's official response can be found at:

http://www-307.ibm.com/pc/support/site. ... 56504.html

I was at work earlier today in an area that has no WiFi for security reasons. As such, I had my IBM 802.11abg card turned off. After working for about an hour, I noticed that the fan hadn't come on. Mobile meter was reading 35-36 on the CPU, which is about normal for my system. Eventually, the fan did turn on, but it only stayed on for a few minutes and turned off shortly thereafter. I thought this was strange because the fan hadn't turned off after starting as far as I could remember. The room I was working in wasn't cold or anything.

I returned home and plugged my ThinkPad into the wall in one of the cooler rooms in my apartment, and turned WiFi on. After 5 minutes of checking the news and email, the fan turned on! CPU temp read a nice cool 34 C. I let my ThinkPad idle for about half an hour and the fan kept running and running, even though the CPU was running at 33 and then 32 C.

So I turned off the WiFi, and a few minutes later, the fan was off! I left WiFi off and the fan has stayed off ever since, even when I used the CPU and the CPU temp went to 37 C!

Edit - Further testing! I ran 3DMark2001SE without the WiFi card turned on. As I expected the fan ran like mad for about 10 minutes after the test finished, but it eventually did turn off! I don't think the GPU is a problem!

Edit - If my system is idle or under modest load (like office work), the fan will come on when the CPU is at 40 C and turn off when the CPU is around 34 C.

I want to see if there's any correlation between having a certain wireless card and having the 'fan always on' problem, so I've created a poll.

[erozsolt]

I don't think this is a perfect solution, because:
- there are people using wifi with a silent T
- I am using a PCMCIA card which is at a different place than the miniPCI slot, and is running usually cool but have this problem.
- When using Wifi running from DC I don't have this problem.

So I think the BIOS uses different curves for AC and DC mod fan adjustment.

[erozsolt]

I posted this in the other thread, but I hope this will be a "final" thread for this problem.

I still don't know what causes the "fan always on" problem, but from my experience:
- The common phenomenon for everybody suffering from this problem: fan is switching on at 34-36 degC and doesn't want to turn itself off for 10+ minutes. After it is off (not usual), it turns back on in 1-3 minutes.
- I think it is a BIOS bug, because this phenomenon is strongly depending on the BIOS version we use.
- What causes the problem is somehow connected to AC/DC mode, because this problem only appears when connected to AC.
- It could be the ATI video chip, because: it is depended on AC/DC mode (PowerPlay feature), and some people have solved the problem after changing the heatsink from CPU-only to CPU-and-GPU cooling version (aka short vs. long heatsinks), but not everybody suffer from this problem using short heatsinks (confused...).
- It could be the wifi card as K. Eng thought in his topic, but very strange that it appears with both miniPCI and PCMCIA cards because they are at different places.

In summary I think that it is not the CPU temperature sensor which causes the fan to run continuosly, but other sensor/sensors which are only visible for the BIOS/Embedded Controller Program

I don't know any 100% fix yet but I think if we mention it to IBM support we might have a chance to have this fixed in the newer BIOS-es.

[K. Eng]

Yes, I agree with you on that completely! I think it is a temp sensor near the WiFi card that is tripping!

In summary I think that it is not the CPU temperature sensor which causes the fan to run continuosly, but other sensor/sensors which are only visible for the BIOS/Embedded Controller Program

The reason I also rule out the ATI chip was because I at one point had Omega Drivers' ATI Radeon driver installed on my ThinkPad, which allowed PowerPlay to be enabled on AC power. This had no effect at all on the fan problem.

However, there is another way to look at it. What if the heat output from the ATI chip + heat output from the WiFi card is enough to trip the sensor? If you use the long fan to take away the heat from the GPU quickly (the heatpipe being more effective than simply downclocking the GPU), the WiFi card may not put out enough heat to trip the sensor.

I have no idea why the PC Card and mPCI would cause the problem. I don't know what kind of controler the PC Card slots use, or what their thermal dissipation is. It is possible that the PC Card controler gets hot when PC Card WiFi is used.

[erozsolt]

Threads regarding this problem:

Silencing Thinkpads - T40 louder than R50e

T40p fan doesn't stop

http://forum.thinkpads.com/viewtopic.php?p=56315

Arggh! how can I get this FAN to go off?

fan runs, hard drive noise

t42 fan running constantly with new bios SOLVED- bug !! (note, SOLVED is a mistyping here...)

underclocking a t42? Very interesting thread!

Fan on most of the time after CPU upgrade

And some older ones...

[erozsolt]

I can't turn the PCMCIA card off by software I can just plug it out. But when I unplugged it, the fan stopped almost instantly!

Good news: if I put my PCMCIA card in the lower slot, it is quieter than in the upper slot!

EDIT: In the last half an hour there was no fan activity with the PCMCIA in the lower slot. I will receive an Intel 2200BG in some days, so I can spot the differences.