# Airflow and Fan Connector Questions



## mrErick (Aug 4, 2009)

Hi All,

First "real" post on here with a question  Looking forward to hearing/seeing all the expert input. I've been winging my mods on my own up until now (successfully!) and figure some advice can only help. I'm stuck in a situation I'm sure many Dell owners have been before...and am lookin for some tips.

*What Started The Mods:*
A few weeks ago my Dell XPS 600 overheated one of my 256MB SLI'd graphics cards...and blew it out. This pissed me off, because I've never changed anything in the "stock Dell" besides additional RAM, I keep my case fairly clean and dust-free, and yet it still lacked the cooling to keep its own stock components healthy. VERY LAME in my opinion, but hey it's Dell. Once my card was blown, I took it as a clear sign I needed to improve the cooling and/or general airflow in the case. 

*What I've Done So Far:*
I went and purchased two 120mm Antec Tri-Cool fans, and installed them into custom locations within the Dell. I cut a hole in the rear bottom of the side panel opposite the mobo, directly in front of where the GPU's sit, blowing cool air directly onto them (or rather "IT" now that I've replaced the 256MB card that survived with a 1GB card). The second fan I installed as an exhaust on the top rear of the case (where it looked like one COULD have been installed by Dell...considering there was a perforated metal case section, with a plastic vent over it....). I figured this way if I added an equal amount of intake and exhaust, I wouldn't create any minor pressure or vacuum levels within the case.

Those fans work like a champ. I was amazed at how quiet they were compared to my OEM case fans, and decided I would replace the 4 internal OEM 92mm fans with Antec substitutes as well. While buying those fans, I noticed a fancy-schmancy little SilverStone FP33 fan controller, and purchased that as well. I then replaced all the stock fans, and wired all 6 new Antec fans to the fan controller (using 3 Y-splitters to hook 2 fans to each channel of the controller). My controller now has the following assignments on the channels: 1: two 92mm Intake Fans 2: two 92mm Exhaust Fans 3: two 120mm Fans (1 in, 1 out). I basically run the PC with channels 1+2 at med/high full time, and channel 3 at low until I get into heavier programs...then I boost the cooling with the two 120mm fans. SO FAR SO GOOD! And if you're still interested enough to be reading, bless you!

*Where I'm Stuck Now, and Need Some Help/Tips:*
Standard Dell OEM fans (on my model at least) connect to the mobo using proprietary 4wire/5pin flat connectors. After doing some google research, I've figured out that the 4 wires are +12V, Ground, Sensor and PWM. Unfortunately since the Antec fans are plugged in via standard 3pin connector to my fan controller (all 6 fans are run through a single 4pin Molex which powers the controller unit)...the Dell BIOS rightfully sees that there are no longer any fans plugged into four critical mobo sockets...and throws me 4 error messages at the bios/boot screen. CPU1, CPU2, Card Case and System fan failures. Press F1 to continue...etc.

Quite simply, I just need to 'trick' the Dell BIOS and motherboard (whatever device actually needs to be tricked, I dunno) into thinking the stock fans are still there. My first idea was to take the Dell fan connectors (I cut them off at the fan...keeping the wires and proprietary plug intact) and connect a small LED to the circuit...thus closing the 12V circuit...and hopefully satisfying the BIOS. It worked fine...and I was greeted with some fancy 5mm LED lights...but it didn't end up working, since the LED obviously doesn't have any connection to the 3rd or 4th fan wires: Sensor or PWM. I think if I could find some way to trick the sensor wire into telling the mobo that the fan is still there and working...I'd be in the clear. Anyone have any ideas on that topic?? What sort of signal is actually sent back along that sensor wire? Is it simply some amount voltage that is interpreted by the bios? If so, I could see about throwing a splitter and possibly a resistor on the 12V wire leading to the LED...and looping it right back to the sensor wire...thus sending back whatever voltage needed to satisfy the bios.

*General Airflow Design, Good/Bad/Tips for a Noob?*
The attachment has a basic idea of what I've done so far. As I noted on there, please don't flame me for the sloppy wiring and cable management...this is ONLY temporary until I am sure everything is working like I'd planned!! 

If you have any general tips to improve my airflow (it's already dropped my operating temps by 4-6° C) I'd appreciate it. Also, any advice on potential ways to trick the BIOS into thinking there are still fans in the stock plugs would be great.


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## Tyree (May 10, 2009)

It appears you've done about all you can with a Dell case. If your temps went down, it worked.


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## mrErick (Aug 4, 2009)

UPDATE! Just in case anyone ever runs into this same problem with a Dell XPS mobo/fan:

To satisfy the Dell Gods, and convince the BIOS/mobo that the four original fans were still working fine, I removed all but the WHITE wire from the proprietary Dell 5pin fan connector, and spliced it into the third wire of the Antec fan (x4). I simply picked the place on the Antec wire closest to the fan plug on the mobo, and spliced the now single-wire/5-pin Dell connector in at that point. A quick melt and some electrical tape...then I plugged the four connectors back onto the mobo in their strange original Dell locations.

In the end I was able to add two new 120mm fans, and replace the original four Dell fans, get a cool blue light show going on inside the case, and drop my temps by about 5°C overall. And yeah, I have that strange feeling I've done about all the poor Dell can handle. It's all held together with 4 screws by Dell anyway with this clam shell case design. If I open and close it too many more times the side's likely to just drop right off, lol.

Anyway, hope someone at some point can use the trick above to cool off their XPS. If you've done any upgrades that would warm things up, you may want to consider adding a few more fans...or risk losing an expensive card or two.


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## pat mcgroin (May 1, 2009)

good work


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