First Fan Mods in a PowerMac G4 MDD Tower
(Power Supply Fan Replacement for lower noise)
by Martin Kaufmann
Published: 8/28/2002
Last Updated: 7/9/2009
(See bottom of page for later updates/other related articles)

Apple announces Pwr Supply Exchange Program to reduce MDD G4 Noise: (From the Friday Feb. 21st, 2003 news - depot.info.apple.com/generic/index.html had details on ordering ($19.95 Shipping/handling fee). Offer runs from Feb 21-April 30th, 2003.

G4 MDD Firmware Update: On Nov. 26th 2002, Apple released a Firmware Update 4.4.8 for the MDD G4s that is to address the fan speed control issues. (Reduce the frequency of the main loud fan kicking into high gear.) A 2002 Apple Kbase Doc (docs.info.apple.com/article.html?artnum=120171) had more info/download link/install guide. (Note: page now shows a date Jan 27th, 2003, although firmware version still 4.4.8 with same change notes.)

(Note: This article was written before the above revised (lower noise) Apple MDD PS/fan exchange kit was offered. The original PS/fans were much worse (louder/horribly irritating frequency) than the later kit parts. The new PS was also a slightly lower max wattage rating than the original PS.-Mike)

When Apple introduced the "Mirror Drive Door" (MDD) G4 towers with newly designed case on August 13, 2002, one of the first questions about the new PowerMac was how quiet would this thing be. Speculation was high that they were quieter due to the addition of many, many holes in the front and back of the case, and the large fan blowing over the massive heatsink.

However, the new PowerMacs are no quieter than the previous generation Quicksilver models. [In fact, when the large fan kicks into high speed, this is the loudest Mac I have ever heard personally as well as having the most irritating noise frequency by far. When the fans are running at max speed, it sounds like a dust-buster(tm) literally-Mike] Why is that? The problem lies not with the design of the case, but with the fans that Apple chooses to stick in these machines. So, I decided to get at the noisy buggers and replace them.

There are a total of four fans in the new DDR PowerMac. One is in the side door and blows on the optical drives when the case is closed. This 60x60x10mm fan is quiet and does not need to be replaced. Another fan is the large one in the bottom of the PowerMac case that blows across the CPU heatsink when the case is closed. This fan is a Delta AFB1212SHE variable speed fan that can spin up to 3700rpm with a maximum airflow of 152 CFM and a noise level of up to 53 dBA. That's a lot of air and a lot of noise. Fortunately, this much airflow is rarely needed, so this variable speed fan is fairly quiet most of the time. (However, with the mod made below, this is now the noisiest fan, so I'm looking to replace it, too.)

The other two fans in the system are located at the FRONT end of the Power supply and push air THROUGH the power supply and out the back. The fans are stacked, one on top of the other, and measure 60x60x25mm. The fans in my system are Delta fans, model AFB0612EH, with the following specifications:
6800rpm with a maximum airflow of 38 CFM and a noise level of 47 dBA.
(Note: the original fan spec PDF file at www.deltaww.com/products/dcfans/pdf/AFB6060254_HIGH.pdf is no longer online)
These fans spin at a constant rate, always putting out 47 dBA of noise. These are the noisy fans of the bunch. So I decided to replace them!

First I needed to remove the optical drives as instructed in the user's manual. Making sure to unplug the AC power cord from the computer first. (After shutting down, discharge yourself by touching the chassis, the disconnect AC cord) Then I removed the one Philips screw inside the case holding the power supply.

PS Retaining Screw
Power Supply Retaining Screw

Next I removed the one torx T10 screw on the back panel of the G4 above the power cable connector. (Note: one reader said his screw was an allen head, not Torx. If the screw has a 'star' pattern inside it's Torx.) This screw not only holds the back panel, but it also secures the power supply. Then you can slide the power supply to the front of the G4 and it will come out.

Rear Panel screw
Back Panel Retaining Screw

I could have released the power cables from the motherboard to completely free the power supply from the G4. I did not do this. Instead, I carefully tipped the G4 on its side, and rested the open door of the PowerMac against a couch. This way I could slide the power supply out and tip it upright and rest it on top of the ATA/100 drive cage, allowing me to access the fans, without all the cable re-routing hassle.

G4 tipped on side
G4 Tipped on its Side for Power Supply Access

With the power supply free, I removed the two screws on top of the power supply, and the three on the side of the power supply, so I could then slide the top/side cover of the power supply toward the back to remove it.

G4 Power Supply
G4 Power Supply

Next I removed the four screws securing the two fans. Then the fans will slide out and I carefully released the connectors from the circuit board they are attached to.

Replacement Fans:
For replacement fans, I chose the fans that come on the Thermaltake Volcano 5 heatsink and fan combination. The fan on these units are an Everflow model F126025DH, which spin at 4550rpm with a maximum airflow of 32 CFM and a noise level of 31 dBA. In my search of dozens of websites and after reading many user reviews, these fans had the best specifications for what I was looking for: lower noise, while still moving a similar amount of air. I believe the slightly less air movement at 32 cubic feet per minute compared to 37.5 CFM of the stock fans is not that great a difference. In subjective tests, with the two fans side-by-side, they seem to put out a similar amount of air. I picked up a Volcano 5 for $9.99 each at my local Fry's. They can be ordered over the web for $6.50 + $6 shipping each from newegg.com if you can't find them locally.

These Everflow fans require a modification to be used in the Power supply. First, I needed to remove the Everflow/Thermaltake fans from their heatsinks (obviously). The next thing I noticed was that the Everflow fans had three wires instead of the two wires that come on the stock Delta fan. I discovered the yellow wire on the Everflow fan is not needed and can be cut off. Then I needed to put the two-prong connector of the Delta fan on the red and black wires of the Everflow fan. I used a small screwdriver to push out the little prongs that held the wires in the connectors. I did this to both the Delta and Everflow fans. Then I swapped the connectors from the Delta fans with the Everflow fans so the Everflow fans will work in the power supply. I did one fan at a time and made sure to note on which side of the connector the black and red wires are to be, as this makes a difference. I put the red wire of the Everflow fan in the same spot of the connector where the red wire of the delta fan was.

Replacement Fans
Replacement Fans and Rubber Isolation Pads
(Each corner of the fan will have a pad)

After performing this minor surgery, I moved the rubber grommets from the old fans to the new ones. These are sure to help keep vibrations, and therefore noise, to a minimum.
Note: There is also a rubber strip attached with adhesive along the bottom of each of the original fans that has to be transferred to the new fans. This strip helps to pad between the fans and pad the bottom fan from the metal power supply case.

After replacing the fans in the power supply, I put it all back together and had a much quieter DDR PowerMac.
(On Dec. 19th, 2002 Martin sent an email regarding 120MM fan replacements in reply to a Dec. 18th news page posting (see below) with a lot of new MDD fan/noise info/links.-Mike)

Hello Mike,
I noticed the note on the main page regarding the noise of the MDD G4's and am glad many people have found my power supply fan replacement article helpful. I wanted to add (and maybe you can post for your readers) that after searching high and low I have replaced my 120x120x38mm case fan.

I couldn't find anything of this size locally with the specs I was looking for, so finally decided to try a few mail order places listed elsewhere on other fan mod pages on your site. I first tried a Sunon 120mm fan that claimed to move 84CFM of air at a dBa rating of 35. This was okay, but just a little too loud for my tastes (but still quieter than the Delta fan at 'medium' speed). I opted for a Panaflo L1A from www.2cooltek.com that claims 69CFM at only 30dBa. This was less air movement, but I found the noise to be very tolerable.

The amount of air the L1A puts out is MORE than the stock Delta fan puts out at low speed, so I figure that the L1A, putting out this same moderate amount of air continuously, would be adequate cooling. Subjective tests after running the computer for hours under a heavy load seemed to show no problems with heat.

That's the mods I've made to my MDD G4 and am very happy. I sure wish Apple would spend the few extra bucks to put decent fans in these PowerMacs.

MDD Fan Replacements Revisited (July 2009)

(Comments updated 7/9/2009)
"I have a MDD G4 (Dual 1.25 FW 800 model, with very long GeForce Ti 4600 128MB video card, USB2 PCI card, 1 optical drive and 2 hard drives) that I am retiring and giving to a family member. It is running Leopard 10.5.7. I couldn't bear to give it to her with the original wind tunnel fans, so I set out to upgrade the fans as per Martin Kaufmann's article on your site (this article - above)
The challenge was that all of the fans he used to replace the G4's fans are discontinued and impossible to find now. After much scouring, I settled on the following models available from Newegg:
$9.99 - Scythe DFS123812-2000 120x120x38mm Case Fan - for the 120mm fan which blows across the CPU - 2000 RPM, 87.63 CFM air flow, 32.91 dBA noise level - as in Martin's article, this pushes less air than the original at its peak, but runs constantly rather than variably - there are a couple of 25mm fans at Newegg which have better specs, but this one must be 38mm to fit.

$3.99 x 2 - PCQUEEN IPC-606010 60x60x10mm Case Fan (item #35-168-003) - for the 2 fans inside the power supply - 3300 RPM, 26.5 CFM air flow, 30 dBA noise level (compared to 38 CFM, 47 dBA before) - original was 60x60x25, but these ones had the specs I needed and fit fine - every fan I found that could push over 30 CFM had noise specs in the 40's dBA, similar to the original fans (no point in switching), so I thought I would gamble on these.

I followed the article exactly, including cutting the unnecessary yellow wires on both fan types, and changing the connectors. The fan mod for all three fans cost $18, took about an hour, and I am happy to report that the sound level is less than half of what it used to be (sounds like about 35-40% what it was before at its quietest), and never ramps up to the full RPM wind tunnel that it did before.

I was a little concerned that the PCQUEEN fans did not have as high air flow as the original power supply fans, but after pushing at maximum CPU load for a full hour and copying with both internal hard drives, the highest I can push the CPU temperature is 60.9 degrees celsius (141.6 F), which is on the high side but within acceptable parameters (not higher than what I've seen with the original fans). I can not make the CPU hit 61 degrees, no matter what I do. The hard drive temperatures are virtually identical to before, even when busy for a long time.

I wish I had measured at full load before the upgrade. Unfortunately I only measured the temperature idling. One note is that I have always had a PCI slot cooling fan in the top slot.

Before fan upgrade, idle:

  • CPU - 56 degrees celsius (note this is an adjacent sensor, not actual internal CPU temp)
  • Hard drive near CPU - 41 degrees celsius
  • Hard drive under optical drive - 32 degrees celsius

After fan upgrade, under heavy load for 1 hour:

  • CPU - 60.9 degrees celsius (141.6 F)
  • Hard drive near CPU - 40 degrees celsius
  • Hard drive under optical drive - 33 degrees celsius

The CPU temperature only dropped to about 60 degrees when the load dropped, so I enabled "Nap" mode
(FYI: There's also a old page here from 2004 on Using CHUD Tools Nap mode to lower CPU temperatures on MDD Towers (includes a Temperature Monitor graph over time) and also updated now with a link a reader's folder of apps for enabling NAP mode (he added as a startup/login item), single/dual cpu switching, disabling Nap mode, etc.-Mike)
Idling, using nap mode:
CPU - 41.1 degrees celsius
Hard drive near CPU - 40 degrees celsius
Hard drive under optical drive - 33 degrees celsius
Dual G4 users have reported problems with nap mode unless the G4 is switched to Single CPU before napping. So... As indicated elsewhere on the Macosxhints site, I use this script to activate nap mode and switch to single CPU:

tell application "System Preferences"
  set current pane to pane "Hardware"
   tell application "System Events"
       if not UI elements enabled then
           display dialog "GUI Scripting is not enabled. Enable?"
           set UI elements enabled to true
       end if
       tell application process "System Preferences"
           set napModeBox to checkbox 1 of group 1 of window "Hardware"
           if value of napModeBox is 0 then
               click napModeBox
           end if
           click radio button "Single CPU" of radio group 1 of window "Hardware"
       end tell
   end tell
   close the first window
end tell

This must be re-run after every new boot. Note that as the original Macosxhints post indicates, though this older version of CHUD tools will work in Leopard, the values it reports for the cache size etc. are not accurate.

So... After all of this and $18 I have a much quieter Mac that runs cooler than before. My only wish is that I would have found a 60x60x25mm fan that pushed mid-30's or greater CFM with only mid-30's or lower dBA noise level. Also, I wouldn't have minded a 120x120x38mm fan that blew above 100 CFM with a mid-30's or lower dBA noise level. If you or anyone else know of better ones I'm all ears! Also, I should note that if someone had 2 optical drives and 4 hard drives (as compared to my 1 optical drive and 2 hard drives) this fan mod might not be adequate.
I hope this helps your readers...
(Updated comments added 7/9/2009)
I have an important update to that G4 fan mod note I gave you.
I noticed that the 120mm fan wasn't pushing as much air as I thought it should, and I realized it was because the 2-pin fan connector on the motherboard wasn't providing enough power. (3 pin connectors typically are for adjustable/variable speeds. But if it's a constant speed fan then maybe the 2 pin wiring was using only 5V vs 12V? (higher voltage = higher rpm fan speed typically)-Mike) I put the 3-pin connector back on and used a 3 to 4 pin Molex adapter adapter to connect it to the 4-pin hard drive power cables -- voila! Lots more air. So... Following the directions in the older article exactly may NOT work depending on the fan you get. Also, using a 3 to 4 pin adapter is much easier than modifying the connector from 3 to 2 pins as indicated in the article.

I also moved the hard drive that was next to the CPU to below the optical bay, because the other hard drive under the optical bay was running much cooler.
Now my updated temperatures WITHOUT nap mode are:

  • IDLE CPU: 51.4 C
  • BUSY CPU after 15 mins: levels at 53.2 C -- much more healthy
  • Hard drive temps: idle 30/32 C, busy 32/35 C

I should note that I also tried a 92mm 50CFM fan right on the CPU heat sink, but this interestingly produced slightly higher temperatures (CPU idle 52.5 C, busy 56.1 C, same hard drive temps). Because it didn't help, I removed it.

With these new results, I am much happier, and would remove my caveat about only having 2 hard drives and one optical drive. I think you could fully populate the drive bays and still be fine.
Cheers, Graham J"

For other G4/MDD Cooling Mods, Case conversions, etc. as well as other Mac models) see the Macs/Systems page.

Other G4 MDD Noise Related Articles/Resources:

(from the Dec. 18th, 2002 www.xlr8yourmac.com news page):

" Mike, your site has been helpful to so many people. Thank you. I know you have run many articles about fan modifications your readers have made to their G4's to quiet them down, most notably the widely circulated Martin Kaufmann article at www.xlr8yourmac.com/systems/g4_mirrored_drive_doors/
noise_reduction/g4_ddr_noise_reduction.html. (this article)
I just wanted to make you aware that after about 200 posts to Apple's own "G4 Usage" forum at Apple.com from owners fed up with the noise and wanting official remedies from Apple, a group of Owners formed at email-list and now a website to organize Owners from all over the world to share info on what Apple is saying, and what resolutions people have been getting. We are tracking Owner's Apple Case #s, and we are writing a letter to the Senior VP of AppleCare, along with Steve Jobs. We are also mounting a publicity campaign via videos -- not parodies of the Switch campaign, but videos that explain the frustrations of professionals in music production, video, medical research, etc, that find the G4 just too noisy to work with.

On the tech side, four things:
(1) A list member has started to so spectral frequency analysis of various G4 MDD's, in stores and in homes, using AMADEUS software. He has managed to pinpoint which G4 interior components are responsible for which frequency sounds. He is looking for a larger sample base to further corroborate. See:
home.centurytel.net/chunhsu/mac/noise/analysis/index.html ("Power Mac Noise - Analyzing")

(2) We are also now working with www.EBM.com, parent company of Germany's Papst Fan company, to find a replacement fan for the very noisey Delta 120mm CPU fan. As you know, several users in Europe have found their G4's become so quiet they only hear their hard drives spinning after installing the Papst fan. But thus far, they have not been able to obtain one that meets the air moving specs of the Delta. But now, working with the parent company of Papst, we are locating the appropriate fan and will be running tests.

(3) The Thermaltake Volcano 5 PS fans can be purchased online from Fry's: http://shop2.outpost.com/product/3051289 (page from 2003 no longer there)

(4) As an alternate to DynaMat
for acoustic dampening foam, others are using: Akasa's PAX Mate
http://www.heatsinkstore.com/akasapaxmate.html (link from 2003 no longer vaild)

WORLDWIDE E-LIST: http://groups.yahoo.com/group/G4noise/
www.G4noise.com (domain gone now)
PETITION: http://www.petitiononline.com/applemdd/petition.html (2003 petition no longer online)

G4 NOISE VIDEOS, so far (links removed as videos no longer online)

home.centurytel.net/chunhsu/mac/noise/insert/index.html ("Power Supply Fan Insert - Instruction")
http://www.g4noise.com/mods/bung.html (page no longer online)
I hope you can spread the word on these "small steps of progress"
Thanks, Richard "

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