Rear PSU Fan Not Spinning

Hi all,
After I finished replacing my old motherboard and CPU with new parts, i started noticing the rear PSU fan (The Front PSU fan is fine) isn't spinning. I remember that before I rebuilt my system, the Rear fan was running fine.

I have no idea why the Rear fan has stopped working unless it has just died but that is not likely. My PSU has been a beast for over 4 years.

Here are my system specs just in case:
CPU: Athlon II X4 635 Quad Core 2.9GHz
MOBO: Biostar A770E AM2/AM2+/AM3 Mobo
GPU: ATI 4670 HD 1GB GDDR3
RAM: 2GB DDR2 (533Mhz) Can't remember what company without opening case
PSU: Antec Smart Power 2.0 (400W)

If it's four years old, it's possible that the fan did finally die.

You could replace the fan, but either way, that PSU is a bit underpowered or a quad with a 4650... might wanna look into just getting a new PSU.

I also recommend the new PSU.

Yeah, I think its either a cable that i didn't plug in when i replaced the mobo or The fan is dead. But the front fan is still running fine. And apparently PSU's are built to run with only the one fan.

You and I might have different views on what Underpowered means. Today almost all new custom-built systems are a complete overkill when it comes to PSU's. I used to have an LGA 775 and a 130W Pentium D. Now I have a 95W Quad Core. I system uses less power than before so how can it be underpowered. The system is getting enough energy to run MW2 on Max settings, 1680x1050 and 2X AA with Vsync on, and still get a solid 78 FPS on average. And the System temperatures whilst doing the above are around 40-53 (My system hasn't gone above 53 degrees Celcius yet). As long as it can do the above I'm happy. So, my question is, will the powersupply be able to continue to do the above and not fry?

That PSU is fine, I'll check my SP 500w 2.0 to see if the rear fan is spinning or not.

You are not drawing even 200w from your setup. Testing my system below (CPU pushed to 3.4Ghz, can't remember voltage setting), I don't even draw 200w from the wall so you can be certain that even at 80%, you aren't using 160w DC. The 4650 is more power efficient than the 9800GT by about 50w on load. Xbitlabs shows it drawing around 30w in 3D compared to 83w for the 9800GT

Thankyou.

I knew that My Wattage was perfect. I knew that 400W was plenty for my setup.

I hate how people get 800W PSU's. They are severely overpowering their system. OVERKILL.

Anyway, So what your saying is without the rear fan I should be fine???

check to see if there is a small 3 pin cable coming off the power supply that is susposed to be plugged in to one of the motherboard system fan connectors.

Yeah i looked for the 3 pin connector. No dice. I think the rear fan is blown. On the upside, i found another Case fan and added it to the rear part of my case and I just Improved my System Temp by about 3-5 Degrees Celcius. I also found a switch hidden under some of the PSU cords that lets me switch the speed of all the fans. they were set to low, and I set them to medium. That also improved my System Temperature by around 5 degrees so now I get an average of 35-40 Degrees Celcius System Temp when Gaming. CPU temp is still about the same (maybe a 2 degree celcius drop)

I'm pretty happy now and I think the chances of my system overheating, even without the rear PSU fan, are slim.

mabey it is too smart

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Unique Dual Fan Technology keeps the SP-500 cool under the hottest action. This revolutionary technology uses two 80 mm fans (one in front and one in rear) to give you quiet, efficient cooling. The first fan (internal and intake) operates when the system starts up. The second fan (external), functioning as an exhaust fan, automatically switches on when the power supply heats up. Modular cable design lets you better organize your cables, so you use only those cables which you want. This streamlines the system and improves the airflow.
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i was pretty sure that i had heard before about a PSU that only kicks in the second fan when needed, and this CraigsList listing says that??

myself i would have to still see it work, by blocking it till it heated up and turned on, before i would be reassured and ignore it for the rest of its life.

Wathnix said:

check to see if there is a small 3 pin cable coming off the power supply that is susposed to be plugged in to one of the motherboard system fan connectors.

Click to expand...

Most of the 3pin connections are just for RPM monitoring, not actually powering the fan.

Nick298310 said:

Yeah i looked for the 3 pin connector. No dice. I think the rear fan is blown. On the upside, i found another Case fan and added it to the rear part of my case and I just Improved my System Temp by about 3-5 Degrees Celcius. I also found a switch hidden under some of the PSU cords that lets me switch the speed of all the fans. they were set to low, and I set them to medium. That also improved my System Temperature by around 5 degrees so now I get an average of 35-40 Degrees Celcius System Temp when Gaming. CPU temp is still about the same (maybe a 2 degree celcius drop)

I'm pretty happy now and I think the chances of my system overheating, even without the rear PSU fan, are slim.

Click to expand...

Do not expect to use the PSU fans as exhaust. In any case, my SP 500w rear fan is also not running. I am only drawing about 55w from the wall though since it's just a Win2008 R2 box with only the following installed

Celeron E3300
Zotac ITX NF610I-K-E
4GB DDR2
2-WD Green 1.5TB (more to come)
Few fans here and there

Very barebones as befitting a home server build.

Psycogeec said:

mabey it is too smart

--------------------------
Unique Dual Fan Technology keeps the SP-500 cool under the hottest action. This revolutionary technology uses two 80 mm fans (one in front and one in rear) to give you quiet, efficient cooling. The first fan (internal and intake) operates when the system starts up. The second fan (external), functioning as an exhaust fan, automatically switches on when the power supply heats up. Modular cable design lets you better organize your cables, so you use only those cables which you want. This streamlines the system and improves the airflow.
---------------------

i was pretty sure that i had heard before about a PSU that only kicks in the second fan when needed, and this CraigsList listing says that??

myself i would have to still see it work, by blocking it till it heated up and turned on, before i would be reassured and ignore it for the rest of its life.

Click to expand...

I have seen it work before, when I used the PSU in another build, during stress testing. There is air movement with just the front fan running.

Alright then. I'm gonna try blocking the front fan for a short time whilst holding my hand over the rear PUS fan so I can feel the heat (so I don't fry it) and to see if the Rear fan kicks in.

A four year old Smartpower 2? Time to replace it. That unit, like most Antecs of that vintage, is full of Fuhjyyu capacitors which were not known to respond well to heat. Due to the rear fan shutting down on these units, the SP2's were the worst of the Antec lot for this problem.

I'm actually amazed it's lasted four years. These usually fried the capacitors in just over one year.