Fan speed 6000 rpm - REALLY new logic board needed?

Fusa

macrumors newbie
Original poster
Jan 24, 2012
2
0
15" - Late 2008 mbp.

Past few months, fan speed almost continuously @ 6000 rpm, CPU usage completely normal.

I've tried:
- resetting Pram & SMC
- Running hardware diagnosis (no errors)
- Controlling speed with multiple applications (e.g. Fan Control)
- even reinstalled OS






It's driving me crazy. Does this really mean I need to spend €800+ on a new logic board for what looks like a tiny broken temperature sensor?

Ideas / suggestions GREATLY appreciated!
 

dusk007

macrumors 68040
Dec 5, 2009
3,386
62
If that is what they told you it is probably true. If no software solution helps hardware is not really repaired just exchanged.

Computer electronics aren't like old cars. You cannot really fix that stuff. You usually identifiy the part that has the fault and exchange it.
The problem is that in a notebook everything sits on the logicboard and it is one piece that is practically impossible to repair if just one thing doesn't work. You have to switch the whole.
A chip that is once soldered to a logic board can never be exchanged at least not with effort that is not much more costly than a new part. I am quite sure it is the same with all the sensors. Especially if it is one of the integrated ones.
Sometimes it is just a cable that got loose by repairs or a contact that is bad, but anything else cannot be repaired. If you nobody took it apart and loosend a cable or attached it badle there is nothing to repair.
 

alphaod

macrumors Core
Feb 9, 2008
22,168
1,212
NYC
The temperature sensor on your motherboard has malfunctioned, so your computer thinks it's overheating all the time and therefore the fans are spinning at 6000 rpm.

The CPU heatsink has a separate sensor on it, so it's possible you might just have one sensor broken on the heatsink therefore you do not need a new motherboard, just a new heatsink (or sensor if you purchase just that).
 

Fusa

macrumors newbie
Original poster
Jan 24, 2012
2
0
You could try clearing dust if there is any
Interesting. I opened up the laptop (for the first time), took out the RAM lats and cleared the dust.

From the moment I booted I could tell the system was way quicker than before. Fan Control responds (this too, for the first time) to my requests and the fans keep their normal pace.

It seems to have done the trick (for now)! Perhaps interesting for everyone with a 2+ year old laptop to clean it out?

Thanks for all the suggestions / comments guys. This forum is wicked.
 

OlyWa510

macrumors newbie
May 7, 2013
1
0
Just replaced my ribbon cable....taxing the MBP (Early 2008) heavily...no fan noise/speed increase.
Previous, replaced the keyboard (after a spill, fast clean up, a few keys not working, no fan issue while the bad keyboard was in) Fan speed while the keys were bad was fine.
Replaced the keyboard and fan speed would go from 2000 to 6000 within 10 minutes of opening Firefox.
No updates, no other software fix, no other hardware change.
Ribbon cable replacement, and voila....not sure why, can't really id the issue other than something wrong with the ribbon cable.
Initially, when I heard about the ribbon cable being an issue on earlier macbooks that were opened up...I tried to reinforce the connection on the mother board with a piece of computer tape and also tried adding a small piece of foam in order to secure the connection.... didn't work.
Ebay+2days waiting+15 minutes of work= reduced fan speed.
All is well, hope this helps.....
 

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