CPU fan speed has started to vary
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From: mm on 29 May 2010 02:16 My CPU fan has started to vary in speed. At least I don't think it did before. It's no big deal to take off the fan again and clean it better, but I'd appreciate your opinions on this anyhow. It's either 4821 or 4991rpm, no other values. I'm using ASUS Probe to measure the speed. It shows a wobbly but basically horizontal line in the graph it gives. Is this bad? Okay, after a few hours the speeds have changed to 4891, 4821, and 4787 rpm. IIRC, it was a straight line, no visible wobbles, until yesterday, when I removed the fan to get "soot" off of the heak sink prongs. There was also soot on the fan blades, which I wiped off pretty well, but maybe I didn't do it completely or evenly where the one blade is overlapped by another. It also seems to vibrate when my finger is on it, which I don't remember happening before. Is this vibration and speed variation really caused by uneven soot? Thanks. (P.S. A) Cleaning the prongs and the aluminum box around part of it did lower the CPU temp by 15 to 20 degrees, so it's below spec now, Now it's usually 138 F. I have an 800 MHz cpu; I forget which brand, on this self-assembled 98/XP computer. I think the fan is 2.25 inches square. B) The soot came from a badly adjusted oil furnace this past winter. It also got on tv screens and some on the wall near the heat output ducts. It's also conceivable that it wasn't badly adjusted but I closed too many first floor registers (3 or 4 out of 4) and this interfered with the combustion, at least they tell me that but I don't see how since the combustion air and the heated circulating air are supposed to be separate. Yet there is no denying the soot, which is also supposed to be in the combustion air, not the rest of the house.)
From: UCLAN on 29 May 2010 14:47 mm wrote: > My CPU fan has started to vary in speed. At least I don't think it > did before. > > It's no big deal to take off the fan again and clean it better, but > I'd appreciate your opinions on this anyhow. > > It's either 4821 or 4991rpm, no other values. > I'm using ASUS Probe to measure the speed. It shows a wobbly but > basically horizontal line in the graph it gives. > > Is this bad? You're concerned by what amounts to about a 3% reduction in measured fan speed? I would guess that your PSU +12v varies by that much. Unless your CPU is showing signs of over heating, I wouldn't fret about it.
From: kony on 1 Jun 2010 22:45 On Sat, 29 May 2010 02:16:49 -0400, mm <NOPSAMmm2005(a)bigfoot.com> wrote: >My CPU fan has started to vary in speed. At least I don't think it >did before. > >It's no big deal to take off the fan again and clean it better, but >I'd appreciate your opinions on this anyhow. > >It's either 4821 or 4991rpm, no other values. I suspect this is just a sampling rate issue, that when the board samples the RPM it does not do it at the same frequency as the fan RPM so sometimes it gets a count of 4821, other times 4991. Either that or it could be as UCLAN wrote, your 12V power rail is fluctuating a little bit based on what the load is on it or the 5V rail. For example a change in video card or CPU power/processing state could make the voltage change some. >I'm using ASUS Probe to measure the speed. It shows a wobbly but >basically horizontal line in the graph it gives. > >Is this bad? > No that is fine... so long as the RPM doesn't drastically lower which could be a sign of an impending fan bearing failure. >Okay, after a few hours the speeds have changed to 4891, 4821, and >4787 rpm. > >IIRC, it was a straight line, no visible wobbles, until yesterday, >when I removed the fan to get "soot" off of the heak sink prongs. >There was also soot on the fan blades, which I wiped off pretty well, >but maybe I didn't do it completely or evenly where the one blade is >overlapped by another. I imagine that by cleaning it you slightly altered its speed a bit, but that it now fluctuates based on what I wrote initially, that the sampling rate of the motherboard is just a little less in sync now. It is not a problem. > >It also seems to vibrate when my finger is on it, which I don't >remember happening before. In that case I would replace it. >Is this vibration and speed variation really caused by uneven soot? That could cause it, or it is spinning faster so the vibration that was there before has grown. You don't need to wonder about this though, you can clean the fan more so you know it isn't uneven soot. > >Thanks. > >(P.S. A) Cleaning the prongs and the aluminum box around part of it >did lower the CPU temp by 15 to 20 degrees, so it's below spec now, >Now it's usually 138 F. I have an 800 MHz cpu; I forget which brand, >on this self-assembled 98/XP computer. I think the fan is 2.25 >inches square. It's old enough I would go ahead and replace the fan, especially if you have a spare fan lying around that is decent quality. If it is the original Intel heatsink with the fan in a plastic shroud it becomes more difficult to replace as a standard fan has no obvious way to mount on it, but you could strap one on with nylon wire ties, or if you are handy in a shop with machine tools you could tap a threaded hole in the heatsink base and buy some long screws from the hardware store to mount the fan... just be sure they don't stick out of the bottom of the sink and keep it from good contact with the CPU or that they short out traces on the motherboard or damage it. > > B) The soot came from a badly adjusted oil furnace this past >winter. It also got on tv screens and some on the wall near the heat >output ducts. It's also conceivable that it wasn't badly adjusted but >I closed too many first floor registers (3 or 4 out of 4) and this >interfered with the combustion, at least they tell me that but I don't >see how since the combustion air and the heated circulating air are >supposed to be separate. Yet there is no denying the soot, which is >also supposed to be in the combustion air, not the rest of the house.) If you have to you can get a fan wet when cleaning it. A small toothbrush with detergent solution on it might be in order, but don't let it sit on the fan too long trying not to get any in the bearing which would dissolve the grease and flush it away. Rinse with plain tapwater, shake out excess, and allow to dry for a day or two before applying power again (or several hours near a fan or vent, etc). However, I'd just replace the fan... even if you get it working smoothly again it is late in its expected lifespan and fans are cheap.
From: GT on 4 Jun 2010 09:21 "mm" <NOPSAMmm2005(a)bigfoot.com> wrote in message news:mha10619dr1ptau8e9mgspv40gv8ja68a7(a)4ax.com... > My CPU fan has started to vary in speed. At least I don't think it > did before. > > It's no big deal to take off the fan again and clean it better, but > I'd appreciate your opinions on this anyhow. > > It's either 4821 or 4991rpm, no other values. > I'm using ASUS Probe to measure the speed. It shows a wobbly but > basically horizontal line in the graph it gives. > > Is this bad? > > Okay, after a few hours the speeds have changed to 4891, 4821, and > 4787 rpm. > > IIRC, it was a straight line, no visible wobbles, until yesterday, > when I removed the fan to get "soot" off of the heak sink prongs. > There was also soot on the fan blades, which I wiped off pretty well, > but maybe I didn't do it completely or evenly where the one blade is > overlapped by another. > > It also seems to vibrate when my finger is on it, which I don't > remember happening before. > > Is this vibration and speed variation really caused by uneven soot? > > Thanks. > > (P.S. A) Cleaning the prongs and the aluminum box around part of it > did lower the CPU temp by 15 to 20 degrees, so it's below spec now, > Now it's usually 138 F. I have an 800 MHz cpu; I forget which brand, > on this self-assembled 98/XP computer. I think the fan is 2.25 > inches square. I would agree with Kony - the wobble in the line is probably just something you didn't notice before. However, if blowing out the dust reduced your CPU temperature by 15-20c, then it must have been very dirty, so perhaps the fan has a little dirt inside and needs another clear out. Perhaps a little dust has blown into the fan rotor and it will fail soon, but even it if does then its not a big deal - fans are easy to replace. even if you can't get one the correct size, you can mount a larger one with a plastic (or cardboard) duct.
From: mm on 6 Jun 2010 01:08
Thanks to you, GT, and UCLAN and Kony. I've been monitoring temps and fan speeds closely and will continue to do so, and it's okay. Plus the Asus Probe goes the front and beeps if any of the two meausred temps, one measured fan speed, or 4 measured voltages gets out of range. Best of all, the variation in fan speed on the diminished after 2 or 3 days and tonight it diminished again and the line is flat at 4856 or 4787**, but there is no visible change to the line! **I presume the variation doesn't really exist but it appears to for the reason Kony gave. Asus-Probe will also keep a history of these measurements, displayed in graphical form, but I didn't start that right away and for what I have the time is compressed so it probably would look flat no matter what. But I may do the other things suggested anyhow, depending on what happens with another partially assembled computer. thanks a lot. On Fri, 4 Jun 2010 14:21:16 +0100, "GT" <a(a)b.c> wrote: >"mm" <NOPSAMmm2005(a)bigfoot.com> wrote in message >news:mha10619dr1ptau8e9mgspv40gv8ja68a7(a)4ax.com... >> My CPU fan has started to vary in speed. At least I don't think it >> did before. >> >> It's no big deal to take off the fan again and clean it better, but >> I'd appreciate your opinions on this anyhow. >> >> It's either 4821 or 4991rpm, no other values. >> I'm using ASUS Probe to measure the speed. It shows a wobbly but >> basically horizontal line in the graph it gives. >> >> Is this bad? >> >> Okay, after a few hours the speeds have changed to 4891, 4821, and >> 4787 rpm. >> >> IIRC, it was a straight line, no visible wobbles, until yesterday, >> when I removed the fan to get "soot" off of the heak sink prongs. >> There was also soot on the fan blades, which I wiped off pretty well, >> but maybe I didn't do it completely or evenly where the one blade is >> overlapped by another. >> >> It also seems to vibrate when my finger is on it, which I don't >> remember happening before. >> >> Is this vibration and speed variation really caused by uneven soot? >> >> Thanks. >> >> (P.S. A) Cleaning the prongs and the aluminum box around part of it >> did lower the CPU temp by 15 to 20 degrees, so it's below spec now, >> Now it's usually 138 F. I have an 800 MHz cpu; I forget which brand, >> on this self-assembled 98/XP computer. I think the fan is 2.25 >> inches square. > >I would agree with Kony - the wobble in the line is probably just something >you didn't notice before. However, if blowing out the dust reduced your CPU >temperature by 15-20c, then it must have been very dirty, so perhaps the fan >has a little dirt inside and needs another clear out. Perhaps a little dust >has blown into the fan rotor and it will fail soon, but even it if does then >its not a big deal - fans are easy to replace. even if you can't get one the >correct size, you can mount a larger one with a plastic (or cardboard) duct. > |