iMac Mid 2007 CPU fan in full blast! Constantly....!

[Nunon311]

Hi all!
For about a month now,on my 24" mid 2007 iMac, the CPU fan is working in full, constantly, and wow, it's loud, unbearably loud..!
I've looked in forums, in apple, everywhere and can't find a solution. (see photo for data)
Most common reason is due to a replacement of the HDD. I didn't...
Here's what i tried so far:
- Physically checked the temp sensors
- Tried to monitor the speed of the fans with "SSD fan control". The speeds remained as shown in the photo.
- Tried to override the control of the fans with "TG Pro 2.50" with no success.
- Tried resetting the SMC. Nothing happened...

I have no more ideas...
Anyone out there can help me?


Thanks!

 

[USB3foriMac]

Possibly the fan control (hardware) circuit is damaged, and it's not possible to lower the speed by any means. There is a Mosfet, Q5700, which could be shorted. If you have a multimeter, measure Ohm between D and S (5 vs 1/2/3/6/7/8). If this is shorted, the only way to restore proper function is by replacing it.
BTW, this is a likely option. Mosfets can get damaged.

 

[zeratul75]

sorry but you did not start from the....starting point......
I mean, did you check if you have any intensive cpu process running?
I would install a fresh new OS in an external usb disk (not a backup....fresh new install, just for testing purpose).
just to exclude any software origin of the problem.....

 

[Nunon311]

Possibly the fan control (hardware) circuit is damaged, and it's not possible to lower the speed by any means. There is a Mosfet, Q5700, which could be shorted. If you have a multimeter, measure Ohm between D and S (5 vs 1/2/3/6/7/8). If this is shorted, the only way to restore proper function is by replacing it.
BTW, this is a likely option. Mosfets can get damaged.
View attachment 1688346

Thank you so much! Will check it out.

 

[Nunon311]

sorry but you did not start from the....starting point......
I mean, did you check if you have any intensive cpu process running?
I would install a fresh new OS in an external usb disk (not a backup....fresh new install, just for testing purpose).
just to exclude any software origin of the problem.....

Thx! Definitely worth a shot. Will do.