Fan starts running at 3600RPM with 44 ºC

Hi everybody,

I have the exactly same problem, same datas for all fans, same GPU diode temp (6°)…on iMac alu 24" (8.1) running under Lion.

I launched a AHT yesterday, wich give me that error code: 4SNS/1/40000001:TGOD-7.875

Regarding some other forums, it seems the logicboard is damaged 😟.

In my case, the trouble happened after moving the iMac from my home to my office (by car).

It looks like the only way to fix it is to replace the logicboard…

Can someone confirm ?

Thanx to all of you…

Hi

I am really sorry to hear this.

I can't speculate on the exact error code offered by AHT but an SNS component in the string certainly relates to a sensor or in a worst case scenario the SMC itself, which lives on the Main Logic Board. One thing is clear, ignoring it can potentially further damage your mac. Don't despair, it could be a hard drive or optical disc sensor for example.

Unfortunately, Apple does not publicly document AHT errors, in specific instances they refer to them as in this unrelated link, http://support.apple.com/kb/TS2081

If you happen to find the error code in full length using Google it will likely come from an unofficial source.

I have to encourage you to bring your mac in to an AASP or Apple Retail Store for an evaluation (visit the retail store page before going to a retail store, a prior appointment might be necessary), apple.com/retail They should be able to tell you more on what the string means after an evaluation.

If you contact AppleCare you may still be under warranty or be entitled for a free repair under their protection plan or a repair extension program. Even if you are outside phone support they are still obliged to help you find the nearest service point.

I don't see anything related but take a moment to see if Apple has any repair extension programs open, just go to apple.com/support and you will find on the bottom left corner a cluster of links titled, "Exchange and Repair Extension Programs". Click on "All Programs". Usually these are covered even if you are outside warranty.

oursjean wrote:

Hi everybody,

I have the exactly same problem, same datas for all fans, same GPU diode temp (6°)…on iMac alu 24" (8.1) running under Lion.

I launched a AHT yesterday, wich give me that error code: 4SNS/1/40000001:TGOD-7.875

Regarding some other forums, it seems the logicboard is damaged 😟.

In my case, the trouble happened after moving the iMac from my home to my office (by car).

It looks like the only way to fix it is to replace the logicboard…

Can someone confirm ?

I had a similar issue with an older iMac G5 where the temperature sensor connector was not seated properly. I doubt that's your problem, but worth a check and certainly cheaper than replacing the logic board.

Hi,

I'm experiencing the same problem with the same iMac (2008, Core 2 Duo 3.06GHz), fan is always at max speed and GPU Temp shows 6ºC.

Apple Hardware Test gave me the same error that oursjeans showed a few post before (4SNS/1/40000001:TGOD-7.875).

Did you solve the problem? How? Was it a Hw issue? If so... Expensive?

Thanks in advance!

Hi everybody,

I solved the issue.

I send back my iMac to Apple,

Hopefully it was not the logicboard, but the Graphic card wich needed to be replace.

Regarding some other forums, It seems that this model nVidia 8800GS often crashes on iMacs.

The cost of the GC today is around 150€, I paid 135€ more for the replacement.

Today iMac is runing normally again…🙂

I hope this will help all of you!

Thx

Thaks for the info.

I'll do the same, let's see what happens.

After all 200-300€ is not too much, isn't it?

@angaros, did you replace the nvidia graphics card? If so, what was the outcome? I have the same problem as you, 6 degrees C on the GPU diode temp, CPU ran running at max rpm, 3,600. Would love to hear your outcome.

Thanks.

After 1 day of searching, I have a solution to the symptom, not the problem.

My Imac24 (mid summer 2008) Intel Core 2 Duo 3.06GHz, 4GB RAM, OSX(10.8.2) w/ the NVIDIA GeForce 8800 GS 512 MB graphics card is showing an unrealistically low temp on the GPU Diode of 6 degrees C w/ a CPU fan running at max rpm of 3,600. Even when the CPU is 99% idle, the fan runs at 3,600, all the time, unless I turn the computer off or put it to sleep. This started about 2 weeks ago. Here's a screen grab from a great little app named, istat pro

I've tried everyting I've read in the forums except for running the AHT (can't find my disk and the D and option D solutions don't work). Nothing worked. I think the problem is a bad temp sensor on the GPU diode as my IMac is fine, except for the CPU fan being on all the time.

Just a few minutes ago I stumbled across this thread, https://discussions.apple.com/thread/2554924?threadid=2554924 and saw the solution to my symptom--a way to actually slow the fan down--written by Jez DK. His solution is genius, send a command to smcfancontrol (download that at http://www.macupdate.com/app/mac/23049/smcfancontrol) that limits the upper limit of the CPU fan. By default, smcfancontrol lets you set the minimum fan speed, but for people with the problem of the CPU fan spinning like crazy when heat is low, we want to slow the fan down. So, install smcfancontrol and issue the following command:

/<path where smc is installed>/smcFanControl/smcfancontrol.app/contents/resources/smc -k F2Mx -w 12c0

That line limits the fan to 1200 RPM. I set my limit to 1400 and here's what istat pro is showing now:

Like I said, this is just fixing the symptom, not the problem. Given that my IMac is 4 years old and is backed up every day, I think this is the best way for me to go. I'm not going to plunk down hundreds of dollars to get this sensor fixed. I may try to do something with automator to see if I can automate the fan speed a bit, so when things do heat up, I'd like to have the CPU fan spin faster than 1400 RPM, kind of like what would happen if the sensor were working ;>

I've had similar problems involving the hard drive heat sensor on two occassions, both of which I repaired myself.

One was simple. I just reseated the sensor plug on the logic board end and everything went back to normal.

The second was with the same sensor, but in replacing the hard drive, the sensor itself was damaged. I was able to obtain a replacement sensor assemply for a few bucks locally (although the first one they sold me was too short).

I suspect my iMac G5 may be easier to work on than yours and your sensor may not be as easily replaced.

Hi, no I didn't...

I'm using the same method you've described, that's smcfancontrol and it's working ok.

But I want to take the iMac to the technical service to fix the problem, just need some free time ;-)

Hi John

Even without running AHT, we already know the issue is hardware.

I gather you have already performed an SMC reset, sorry but this looks like a long thread so I apologize in advance if I am repeating previously offered steps.

If you have, reducing fan RPMs, as you said is clearing the problem and not the symptom.

I just want to throw a word of caution. To make a long story short, do get it serviced, find time. Until then, make sure that the iMac is not overheating as it could be a safety hazard - in other words keep your eye on it. I doubt anything will happen, God fobid but it's best to be safe.

I hope this helps and I hope you find time to get the unit diagnosed.

Kind regards

By the way... I never slow down rpm too much, usually I set it to 2500, it isn't too noisy and I think it's better than 1200-1500 rpm. Anyway I must take it to the service as soon as possible.

Hi John,

I have the exact same iMac with exact same problem and would like to tweak the max rpm speed on my cpu fan as per your good suggestion.

I've downloaded the smcFanControl.

But how exactly do I issue the command (/<path where smc is installed>/smcFanControl/smcfancontrol.app/contents/resources/smc -k F2Mx -w 12c0) as you describe?

thanks,

Michael