Macbook fan and temperatures, is there a problem here?
October 5, 2011 3:51 AM   Subscribe

The wife was working on her Macbook Duo about a week ago, when the screen when dark for about 10 seconds and perhaps a slight pop was heard (she isn't sure). After the screen came back on the fan seemed to stop working. Normally, she could cause the fan to run pretty loudly as she Netflixed, played video or Flash games. After that noise, the fan no longer ran that loud or fast.

I installed Fan Control and it said the left fan was fine, running at various speeds, while the right fan was -1 RPM.

Ok, didn't know a Macbook had two fans, but I ordered the only one that was available for my model on iFixit and installed it.

Same "problem". Fan control says the right fan is moving at -1 RPM. There is no loud fan noise, even when doing activities that use to cause the fan to spin loudly.

The computer works fine, but the temperature on the CPU and Airport card climbs after a while (according to iStat Pro). The RPM of the (one?) remaining fan steadily climbs, but doesn't seem to go over 3000 RPMs after 10 minutes.

So is there an actual problem here? I replaced the fan, have physically verified that it's running when I took the laptop apart. I don't know what to do next or even if there's a problem. The computer runs perfectly fine, though we've only used it small doses (10 minutes here and there) for fear of overheating the machine.

Is there a specific temperature range I should be worrying about in regards to the internal components?

Is it odd that fan no longer spins up loudly?
posted by Brandon Blatcher to Computers & Internet (8 answers total)
Download SMCFan Control and manually try out the fans; it'll report the temperature as well as individual fans (two).

I suspect that one fan is dead.
posted by filmgeek at 4:06 AM on October 5, 2011

Have you tried an SMC reset?
posted by procrastination at 4:58 AM on October 5, 2011

Sounds like the speed controller and/or the speed sensing circuit has "popped".

Wait, did you verify that the other fan was running?
posted by gjc at 5:09 AM on October 5, 2011

Correct me if I'm wrong, but I don't think you have much to fear of "overheating" the machine. If it gets into redline temperature it'll shut down to prevent damage. I'd worry about losing work more than I'd worry about hurting the laptop.

You're being prudent and that's admirable but I think you should be fine. Note, I've never worked on Macs at this level before but that's how other laptops I've worked on behaved.
posted by RolandOfEld at 8:14 AM on October 5, 2011

Wait, did you verify that the other fan was running?

What other fan? I only see one, iFixit only lists one fan as a replacement part.

Is there one or two fans in a Macbook? If two, which fan is the one I replaced (the big one on the logic board)?
posted by Brandon Blatcher at 9:01 AM on October 5, 2011

The 'right fan' reading is most likely due to the fan control circuit having the capacity to run two fans, or there being two fan connectors on the board. My (desktop) motherboard reports 6 fans with 4 of them running at 0 rpm, and I only have two. I think your fan is fine, good job on replacing it. You could run the Apple Hardware Test if you want to reassure yourself that everything else is running as it should.
posted by fearnothing at 9:45 AM on October 5, 2011

I think SMC fan control also tells you the temperature. If not, I'm currently using iStat on my several-years-old Macbook pro and it shows the temperature of several internal components, as well as fan speed, so that's another option. According to at least one source on the Mac support forums, the internal temperature spec is 30-90 degrees C. RolandofEld is also right about the machine shutting down to prevent damage due to overheating. Of course, you don't want to do that often, but if it were MY computer I'd absolutely be doing everything I normally do with it, keeping an eye on the temperature, and seeing if it shut down. (The only reason for keeping an eye on the temperature being to figure out at what point it shuts down, so you can stay below that otherwise).

I bet you only have one fan. If you only see one fan to replace, and the instructions and pictures on iFixit for replacing the fan only show one fan, there's probably only one fan. My MBP does have 2 fans, and iFixit shows 'replace left fan' and 'replace right fan' both as options.

As far as the initial issue - it's possible something happened with your temperature sensor, and so the fan speed isn't responding to changes in temperature. If the fan isn't speeding up properly, that's what I'd guess. So then you'd see the temperature sensor give a weird value or be non-responsive, and the fan speed wouldn't change properly. If you find the computer is running hot and the fan not responding, you can use SMC Fan Control then to set the fan to a higher speed - it'll be loud all the time instead of just some of the time, but it'll be better for the computer. You can also look in to the various other overheating solutions out there - only putting the laptop on hard surfaces, etc.
posted by Lady Li at 11:57 AM on October 5, 2011

As others have mentioned, just run it like you normally do. The fact that your fan speeds up under load is a good sign, as the temp sensor seems to be working. You could use the software to wind your fan up to 100% - is that the same rpm you see when the computer is running hard? If so, then everything is working just fine. If it's not, does the computer go unstable etc. at high loads, then you have something to worry about.

The cpu has internal thermal overload protection, and will lock up (crash) if it's overheating. Just turn off the machine and let it cool. It's been many years since you could actually overload a cpu to thermal failure (looking at you AMD..athalon?) back in the early 2000's.
posted by defcom1 at 2:24 PM on October 5, 2011

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