Mac 3,1 Pro (early 2008) CPU Fan Reading "0"

[pdafan]

Hi all,

I just bought a pre-owned Mac Pro 2008 over the weekend.

Using iStats Menus Pro, I observed that my CPU Fan Reading is 0 while the rest e.g. (Exhaust, HD/Expansion, Power Supply) are giving normal range of 599, 799, 846 rpm respectively.

Yet, the bottom fan (of the 2 front fans) is spinning fast with very loud noise.
The CPU temperature from iStats is reasonable at 37C to 70C.

There are also some observations from several tests I have done.
a) When I detach the front fans from the power, the whole unit is quiet. This confirms the noise come from either of the 2 fronts fans.
b) When I disable the top front fan (detach power), the top fan stops spinning and unit is very noisy with btm fan spinning.
c) When I disable the btm front fan, the btm fan stops but with the top fan still spinning. The unit is quiet.

(a) (b) (c) prove the btm fan is the culprit. There are 2 possibilities:
- the physical btm fan is faulty
- the physical fan is functional but is being instructed to spin at top RPM.

I further connect the signal cable for top fan to the btm physical fan and left the top fan detached. Upon boot up, the btm fan is spinning nicely and quietly.
This confirms the btm fan is working fine which means to say that the reading sent to the btm fan is erraneous causing it to spin at probably the highest RPM. YET, iStats shows CPU Fan rpm is 0.

I suspect that the m/b is not giving the right temperature to the fan unit, thereby wrongly instructing the fan to spin wildly.

Any advice from experts here to help resolve this issue?
Thanks in advance.

 

[gugule]

Have you solved the problem of CPU fan?

Hi pdafan,
I found a problem like yours.
I also bought a pre-owned Mac Pro 2006(1,1) last week. In the several days before today, it ran normally. But today it runs with loud noise.
Using istats pro, I observe that HD/Expansion Fan Reading is 0 while the rest three fans are spinning normally. Unload the side panel of the machine, I find the top front fan is spinning fast and blowing strong wind.
I think this problem is the same as yours. The only difference is that my problem is the top front fan while yours is the bottom front fan. The system can't read the speed value of the fan, so it keeps the fan in its maximum speed to protect the machine.
So, have you solved the problem? If yes and you have the time, please let me know how you solve it. My e-mail is gugule@163.com. Hope to receive your letter. Thank you very much.

 

[gugule]

Here is the picture from istat pro.

By the way, I want to tell you a sad thing. When I took the front top fan out and tested it, I made a mistake. I got the positive pole and the negative pole in wrong place. Then the fan broke up. It never runs again. I have to buy a new one to replace it.
So be careful and don't make mistakes like me.

 

[markolomew]

I bought an early 2008 Mac Pro as well, and gave it a good cleaning. The front fans are still unbearably loud. Did anyone ever find a fix???

 

[h9826790]

The front fans are still unbearably loud.

What's the RPM?

 

[markolomew]

What's the RPM?

iStat Pro readings:

CPU Fan: 499
Exhaust: 1550
HD/Expansion: 2856
Power Supply:599

I've double checked it with smcFanControl and got similar:

CPU_MEM: 498
IO: 2851
EXHAUST: 1549
PS: 599

I've reset pram and smc, neither did anything.

 

[h9826790]

1) Try reset SMC again and check if the number changed. >2000RPM is way too high.

2) May be graphic card related. Load it up (e.g. run LuxMark), and wait for few minutes to check if it back to normal idle RPM.

 

[markolomew]

1) Try reset SMC again and check if the number changed. >2000RPM is way too high.

2) May be graphic card related. Load it up (e.g. run LuxMark), and wait for few minutes to check if it back to normal idle RPM.

Is there a way to hard reset smc? I've followed the soft method of powering down the mac pro, unplugging it, waiting 15 seconds, plugging it back in, wait 5 seconds, power on.....but it does nothing. Is there another method I'm not trying?

I'll try the LuxMark shortly.

 

[h9826790]

Is there a way to hard reset smc? I've followed the soft method of powering down the mac pro, unplugging it, waiting 15 seconds, plugging it back in, wait 5 seconds, power on.....but it does nothing. Is there another method I'm not trying?

I'll try the LuxMark shortly.

This is the correct procedure to reset the SMC.

Other than LuxMark, you may simply use SMCFanControl to set all the affected fan (I/O and Exhaust) to full speed, wait for 10 seconds, and then set it back to idle. This is a little bit quicker than use LuxMark, but the fans may still need few minutes to spin down.

 

[markolomew]

This is the correct procedure to reset the SMC.

Other than LuxMark, you may simply use SMCFanControl to set all the fan (I/O and Exhaust) to full speed, wait for 10 seconds, and then set it back to idle. This is a little bit quicker than use LuxMark, but the fans may still need few minutes to spin down.

Sadly I did that too. I put each of the fans individually up to max and saved the setting. Then I waiting until I could audibly hear the fan increase, then put it back down to the lowest setting. This worked for all fans except the IO fans setting. It didn't matter what setting I put it at, it stayed max speed.

 

[h9826790]

Sadly I did that too. I put each of the fans individually up to max and saved the setting. Then I waiting until I could audibly hear the fan increase, then put it back down to the lowest setting. This worked for all fans except the IO fans setting. It didn't matter what setting I put it at, it stayed max speed.

If 2800 is the 3,1's IO fan max speed (on my 4,1, the expansion slot fan max at 4500), it may be an indication of temperature sensor failure (or real hardware problem). e.g. A sensor fail to report temperature may cause the fan spin at full speed to protect the hardware from overheating.

 

[markolomew]

Took off the heat sinks to clean them out and noticed the heat sink compound looked pretty shotty. Just picked up some more and will apply it. Maybe this is the issue. Where are the temperature probes located on this logic board?

 

[markolomew]

So took everything out, cleaned all the thermal compound off, added new, reattached and booted up. No love. The top fan is the only one that has this issue. On boot, the video card fan kicks on then about 3 secs later the IO fans kick on. The bottom stays solid speed but the top ramps up to max; sounds like a plane taking off.

It's specifically the top fan only. Do you know what temperate probe this is tied too?

 

[markolomew]

ok, the ONLY thing I can get to make any difference is to download the program "Macs Fan Control". At first I manually set the speed to the IO fan to 800 and it instantly worked. Problem is, I am not really sure how fast of rmp's this really needs to be, so I decided to tie the speed to match the IOH Heat Sink. Not sure if this is what I need to do, but I thought "IO Fans" ... "IOH Heat Sink"...sounds close enough. The RPMs got bumped up to 1550, and I hear it running, but it's not bad at really. It's like a really light oscillating fan.

What RPMs should I be shooting for here, or should I tie it to a certain part (see image)?

EDIT:
When I reboot, the fan kicks up to 2800 rpms. It stays like this until the fan control program auto loads after the mac desktop loads up, then the speed kicks down to whatever I preset it to. This shows me this fan program is just masking the problem, not really fixing it.

 

[nigelbb]

You reset the SMC but you didn't reset the PRAM with the CMD-Option-P-R Power on finger trick. Give that a whirl.

 

[markolomew]

I've reset pram and smc, neither did anything.

Unfortunately resetting pram didn't work either.

 

[markolomew]

Just ran the apple hardware test and got this error code. Anyone know what that means?

 

[h9826790]

My understanding is that the SMC (System Management Controller) itself failed. Since you've already perform the SMC reset more than once. This code is quite possible indicating a real hardware failure (or partial failure).

 

[markolomew]

My understanding is that the SMC (System Management Controller) itself failed. Since you've already perform the SMC reset more than once. This code is quite possible indicating a real hardware failure (or partial failure).

Yup, I think you are right. I just spoke with an online apple tech and gave them my error code. Turns out that means SMC is dead somewhere along its path and I have to take it in. Ugh. Nothing like carrying a heavy mac pro through a ghetto mall.

Anyway, here is the direct word from the service guy:
"Ok that error message is related to the system management controller. The SMC is the hardware responsible to sending power to the rest of the computer. If certain hardware isn’t getting enough or is getting too much power it can cause performance issues"

UPDATE: I just back from the Apple Store. They no longer work on any "Legacy" macs and instructed me to seek out help at a 3rd party like Fry's or MicroCenter. Upon pressing the genius more, he said that the failure of SMC is not something they swap out individual components for....they say this is a "complete logic board replacement". HUGE expense right there. Nope, no thanks.