Fan runs hard only while hibernating

[Hastor]

I have a Macbook Pro and the fan behaves normally when it is just running, can barely hear it. However, anytime it hibernates, whether it is closing the lid, or due to idle time, the fan kicks into high gear, running very loudly. When it is woken again, the fan slows down to normal once more.

Have replaced the hard drive (last one died) and installed Snow Leopard with the disc that came with it, so we have a fresh install of the OS on a brand new drive, and this still happens. I've tried some of the normal approaches, tried changing hibernatemode to 0 or 2, tried resetting SMC. Nothing seems to help. Was hoping the OS reinstall would, but no good. I would think the fan was faulty, but since it is only happening while hibernating, it seems like something must be telling it to run. It causes the battery to drain when it shouldn't, and is just very loud and annoying, waking us up at night if we fall asleep with the pc on and it hibernates later.

Does anyone have any suggestions as to what might be causing this, or how to fix it? I've seen similar stories online, but not where it is happening even after an OS reinstall.

 

[Kaveman]

If you have just reinstalled the OS, it might be Spotlight reindexing your HD and every time you stop it it has to start again???

 

[Hastor]

I dont think so because the fan is running high ONLY when its hibernating, stops once you wake it. Also was doing this before the os reinstall. Just thought the reinstall may fix it which it didnt. Like i mentioned, new hdd so completely clean install. Havent added anything.

 

[Kaveman]

Was it doing this before the new HD?

 

[Hastor]

Yes, was doing this before the new hdd, before the os reinstall, etc. It was doing it a few months ago but when i used pmset to change hibernatemode to 0 it quit. Then it started back a couple months later, still with the old hdd. Hdd was getting real hot and died. New hdd isnt getting hot though.

 

[Kaveman]

It might have cooked a sensor.

This does not sound like something you are going to fix yourself, take it to an Apple service Centre near you.

 

[Hastor]

I thought about that, but wouldnt a cooked sensor also cause it to run when not hibernating? It Only kicks on hard when the screen is disabled and the led is pulsating. It slows to normal as soon as it is woken again. If it mistakenly thought it was hot, it would continuously run. Something about hibernating is triggering this.

 

[Kaveman]

when the lid goes down there are different sensors or levels used. So no.

If you replaced the HD and Software then it must be another component. It's not the OS.