high fan speed

Replaced hd in an Imac, and installed MtLion. Since then, fan runs at 3500, is pretty audible (before - in Leopard - smcfan ran it about 2000, quietly.) Smcfan is reinstalled, shows the higher speed, resetting fan to lower speeds in smc does not "take" (remains same). Temps running nicely low at this speed, but noise is irksome and I worry about fan life running at max. Any fixes?
Thanks

OK I was just about to suggest the SMC fan control software and had originally provided a link but see you have done that already. The controller for the fan motor will still have it's max voltage with lower variations in between that should be able to be controlled by SMC, but it would appear in your case that MtLion is more resource hungry than Leopard and the higher fan speed is actually need to ensure the extra heat generated by the chips is dissipated effectively.

How much RAM are you running in that machine?

MickMac99 said:

but it would appear in your case that MtLion is more resource hungry than Leopard and the higher fan speed is actually need to ensure the extra heat generated by the chips is dissipated effectively

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Nope! Wrong answer.

Mountain Lion, being highly optimized for Intel, is LESS resource-hungry than Leopard. I suspect the real problem is an outdated or improperly-uninstalled version of SMC hanging around, it's a bad program and causes more problems than it fixes IMO.

I would suggest a clean install of Mountain Lion and for the user to stop mucking about with Apple's delicately-tuned automatic fan control. There's NO need for users to "manage" the fans in normal use.

replies

The Mt lion was a clean install, on a new hd. (and thus the scmfan was a new install to that same new hd - there being just the one on my machine.) In point of fact, the fan was running at the speed I mentioned (this I'm judging by the sound it was newly making under the MtL, before I installed the scmfan software,that was why I tried it - it simply allowed me to see the speed. I am Running 4 G ram. I just uninstalled the scmfan as a test, but the new, higher, sound level is the same - indicating to me that the speed of the fan is the same.

Does the machine have it's own way (accessible to me) of regulating fan speed? If the MtL produces less heat, I should be able to lower levels of speed and sound.

And a question I might be asked, the old hd was a 5 1/2 WD and it was replaced by a hybrid laptop drive that by all rights produces less heat as well.

Sound is humming along...


Thanks, mafac

And a question I might be asked, the old hd was a 5 1/2 WD and it was replaced by a hybrid laptop drive that by all rights produces less heat as well.

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All the above answers have not taken in account the heat sensor which must be placed on the new drive. Also, since the drive you used is a hybrid laptop drive, it's likely the heat sensor is not working right.

When replacing the hard drive in an iMac, consideration must be given for the type of drive. It's very likely that you're going to need to yank that hybrid drive out and replace it with a standard 5.25" SATA drive (5400 or 7200 RPM) in order for the heat sensor to control the fan speed properly. SMCFanControl is not going to work.

heat sensor

heat sensor was reapplied to new drive... as new drive ought to run cooler than old one, didn't think this could be issue. Plus, temp of cpu fan runs at 34C, so ought not fan lower speed (if sensor shows cooler than necessary, why would fan be called upon to stay high?)

And an addendum... what is downside of fan working at higher speed and temp running lower than normal (I assume fan life would be a bit reduced, but by how much?) I also assume temp is like being too rich.. can't be too cool. Sound is the issue of course.

heat sensor was reapplied to new drive... as new drive ought to run cooler than old one, didn't think this could be issue. Plus, temp of cpu fan runs at 34C, so ought not fan lower speed (if sensor shows cooler than necessary, why would fan be called upon to stay high?)

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We've seen this before with the iMac. Either the heat sensor is not working right or that hybrid drive is running warmer than you think it should be.
The temperature of the CPU fan and or the optical fan has nothing to do with the hard drive fan or sensor. Each operates independently.

And an addendum... what is downside of fan working at higher speed and temp running lower than normal (I assume fan life would be a bit reduced, but by how much?) I also assume temp is like being too rich.. can't be too cool. Sound is the issue of course.

Click to expand...

No downside really except as you say - it's loud and may be disturbing to you.
As far as reducing the life of the fan, I'm not sure it does. As long as it doesn't bother you (louder) I would leave well enough alone.

Junk in, junk out... My error resulted in my problem. Kudos to chscag for guiding me into thinking about the heat sensor. Though I made all the correct moves on reassembly, I apparently dislodged the connector while reinstalling the cover. Clipped back into pins, carefully replacing cover, and I'm good to go with low temps at a low fan speed. Thank you chscag; and thank you all the others who gave me help as well.

Thanks for posting back. Enjoy that new drive and visit us often.

Well done to both of you!