Fan continuously runs at 6200 RPM

[cubeeggs]

I have a late-2006 MacBook (2.0 GHz Core 2 Duo Merom) that has been serviced several times. It’s had the fan replaced twice: once in the summer of 2007 because it completely failed, and once in the summer of 2009 because it had been making clicking noises. The logic board was replaced last November because of some minor issues with the headphone jack, along with the LCD which had some gray dots starting to appear.

I’m not sure how long it’s been doing this, but the fan seems to be running way faster than would be normal. The fan never seems to run below 5000 RPM, and once the CPU warms up, it seems to run continuously at 6200 RPM (the maximum speed). smcFanControl (set to Default fan speed, the minimum) usually reads the temperature as being between 145 and 155 degrees Fahrenheit. I took the keyboard off yesterday to clean dust out of the fan, but it didn’t seem to do much. I’m pretty sure this isn’t a software issue, because the fan also seems to run a lot when the MacBook is booted into Windows 7, although I’m going to try booting it from the OS disc and an external hard drive just to be sure. I’ve tried resetting the SMC, and I’m pretty sure I tried resetting the PRAM a while ago. The only remaining thing I can think of is that when the repair tech replaced the logic board, he didn’t apply the thermal paste properly (the optical drive was replaced even though it was working when I sent my MacBook in, two hinge screws were overtightened, and the bezel was not installed properly).

Are there any other things that could be causing my MacBook to not cool properly? If booting from another copy of the OS doesn’t change the fan speeds, I’m thinking about taking the heatsink off this weekend and applying some Arctic Silver.

 

[cubeeggs]

I just tried booting from an external hard drive with Leopard installed. The fan started at around 4000 RPM when I first started monitoring it but now it’s running at about 1800 RPM around 130–135 degrees. If the fan speeds up again when I boot back into Snow Leopard, should I reinstall the OS?

 

[cubeeggs]

I booted from the internal drive running Snow Leopard and the fan went back up, so I booted from the external drive again and the fan won’t go down now. I’m thinking it must be a hardware issue.

 

[Giuly]

Reset the SMC and fix permissions via the Install-DVD.

 

[cubeeggs]

I’ve tried resetting the SMC and repairing the permissions while booted from the hard drive. I’ll try repairing the permissions from the install disc, but I don’t think that’s the problem.

 

[Pax]

Run Hardware Test (on your install DVD)

In particular look for failed temperature sensors. If the Mac detects a faulty sensor it can go into fail-safe mode where it runs the fan at full speed regardless of internal temperatures.

Sensors are cheap to fix. It could be as simple as the sensor connector not being plugged into the logic board, or a broken wire. You having had a logic board replaced might make this a likely culprit.....

 

[blackburn]

Yep when swapping hdd's on iMacs and not plugging the temperature sensor makes the fan run at full speed so I agree with Pax since macbooks should do the same to prevent them from overheating

 

[cubeeggs]

I don’t have the discs with me right now, but I have Temperature Monitor open and it’s giving me readings for

CPU A Temperature Diode
CPU Core 1
CPU Core 2
Enclosure Bottomside
Main Heatsink 1
Main Heatsink 2
Memory Bank A Point 1
Northbridge Position 1
Northbridge Position 2
SMART Disk ST9500325AS with the serial number in parentheses

and they all look OK. I’ll try running the hardware test but all the sensors look OK. Interestingly, the heatsink is under ten degrees cooler than the CPU, so the thermal paste doesn’t seem like the issue. I’m wondering if something’s obstructing the fan, because I think I should be feeling more airflow out of the vent when it’s running at 6200 RPM.

 

[Pax]

Re sensors: We had a previous similar case, and in that case there was one "hidden" temperature sensor which iStat Pro didn't report, on the heatsink near the fan. I don't know if Temperature Monitor has the same blind spot as iStat Pro, so it's probably worth checking with Hardware Test too.

Re fan clogging: if you are using the stock fan control algorithm the fan shouldn't ramp up until your CPU is nice and hot, or another component is very hot. If your CPU is at less than say, 60 C, the fan should be idle (exact temp will depend on model I suppose). So what I mean is:- if your fan is at 6200 rpm and your CPU is <60 C, you probably have a fan control algorithm problem. If your CPU is >>60 C, you may have a clogged air flow problem. But you are right, you should feel a good air flow on the back of your knuckles with the fan at 6200 rpm.

Another thought:- we had a another case where someone had swapped their HDD and the new one had a short circuit which made it run very hot. This caused the fans to run very fast. So another hot component could be the problem.

It's worth posting your temps on here for all components, see if anyone has any bright ideas. Just paste it from Temperature Monitor. Make sure the Mac is idle though.

 

[cubeeggs]

I uninstalled rEFIt, reset the SMC, repaired permissions from the install DVD, ran the extended hardware test (everything passed), reset the SMC again, did a double reset of the PRAM, and booted off the hard drive again. The fan stabilized at about 5200–5300 RPM.

 

[cubeeggs]

I think I’m going to try removing and replacing the fan tomorrow so I can see if anything under it could be causing an airflow problem.

 

[Pax]

I think I’m going to try removing and replacing the fan tomorrow so I can see if anything under it could be causing an airflow problem.

Worth a try

I would say your temps are "normal to high" for a MB at idle with the fans at 1500 rpm.
But if your fans are at 6200 rpm your temps should IMHO be a lot lower.

So maybe cloggage is the problem

 

[cubeeggs]

I managed to remove the fan and it looked like about 50% of its rear vent was clogged with dust, so I removed it and after a couple of tries managed to get my MacBook back together with everything attached.

It maybe feels like there’s a little more air coming out of the vent, but it doesn’t really seem to have helped very much. I’m using my MacBook on my lap right now and the fan’s spinning at 6200 RPM and the CPU’s measuring at 72 degrees Celsius (161.6 degrees Fahrenheit). The CPU’s at about 45% utilization right now.

Interestingly, the first time I tried booting after I cleaned the fan, I noticed that I hadn’t reattached the fan cable properly and it wasn’t running at all. I only kept it on for about a minute, but the processor was measuring about 135 Fahrenheit with the fan completely off.

 

[Pax]

I’m using my MacBook on my lap right now and the fan’s spinning at 6200 RPM and the CPU’s measuring at 72 degrees Celsius (161.6 degrees Fahrenheit). The CPU’s at about 45% utilization right now.

Hmmm. The problem with the old MBs (I have one) is that the fan goes from idle to spinning like crazy over a very small temperature range somewhere in the mid-70s.

I put my 2006 CoreDuo 1.86 GHz under 50% CPU load and got the the fan up to 6200 rpm with the CPU in the mid-70s C. So I can believe that a continuous CPU load of 45% is enough to get 6200 rpm / 72 C.

At idle my CPU is low-mid-50s C with the heatsink high-40s C and the fan at 1500 rpm. So a little cooler than yours. But only a couple of C

But I really don't understand why your fan is so fast at CPU idle, even though temps look normal.

 

[cubeeggs]

The fan starts at about 3000 RPM when I first turn the computer on. I guess I’ll try booting from the external drive again.