Just a quick query

I have just refurbished an older XP machine and a trying out multiple drives in it.

Now my only problem is the CPU fan runs flat out all the time and I cannot workout why. The BIOS doesn't show me any CPU temps nor does Speccy and the only one I can get any readings whatsoever is the HWMonitor .

At first I thought maybe it was the stock cooler and so fitted a Coolermaster TX3 with no change the noise from the fan was so intense I swapped it out for an ordinary case fan which is quieter but still flat out at speeds in excess of 2000 rpm.

In the HWmonitor shot I can see diodes 1 & 2 and the internal one and what I am presuming is the temp of the core (Intel Pentium 4 630 - single core two threads).

I have disabled the CPU fan in the BIOS but that did nothing so I enabled it again and now I ma just out of ideas except perhaps the board is not communicating with the CPU?

So has anyone got any suggestions please?

John, my only suggestion is to see if speedfan would work for you. But, I suspect it won't. If the monitoring programs can't read the diodes, they will have trouble controlling fan speed based on temps. Those older Pentium CPU's are low power but seem to run pretty hot. I have one. If all else fails, a fan controller may help, there are some simple ones that will control it. There are some for 1 fan that is external. The Thermaltake Frio is a big cooler and the fans are pretty loud, but they have controllers on them, you just have to reach inside the case to turn them up or down.

essenbe said:

John, my only suggestion is to see if speedfan would work for you. But, I suspect it won't. If the monitoring programs can't read the diodes, they will have trouble controlling fan speed based on temps. Those older Pentium CPU's are low power but seem to run pretty hot. I have one. If all else fails, a fan controller may help, there are some simple ones that will control it. There are some for 1 fan that is external. The Thermaltake Frio is a big cooler and the fans are pretty loud, but they have controllers on them, you just have to reach inside the case to turn them up or down.

Thanks Steve I will try that Speedfan and I think I have a spare recycled Thermaltake fan controller somewhere otherwise I can fit a resistor in when I can get to working out the Ohms value for it and fit it into the power cable.
It is annoying more than anything else as I find Coolermasters are usually fairly quiet. (Coolermaster TX3 cooler) :)

John, don't I remember you buying some Noctua fans? If so, they came with resistors you don't really use, or at least don't need.

essenbe said:

John, don't I remember you buying some Noctua fans? If so, they came with resistors you don't really use, or at least don't need.

No I didn't buy any Steve but my son has one that he didn't fit when he did his build so I guess I can take a look at that.

By the by I tested a 1 watt 39 ohm resistor on the Coolermaster fan (0.6A) and it ran perfectly until it burnt my fingers sobbing aside LOL!! it appears that it would take a 39 ohm resistor at least at 5 watts (and wirewound) to absorb that amount of energy so there must be a trick in using those small resistors one sees in those speed adaptor cables like this one 4-Pin Fan Speed/Noise Reduction Cable
although I do see that the resistor actually sits in the 5v rail wire whereas I was running that "hot" one in the 12v connector.
The only other solution is to use some of that bar heater wire that glows red when the heater is switched as it is made from a special wire that has an inbuilt resistance per metre.
It is made from an alloy of nickel and chromium - usually and because of the resistance is worked out (the length of the winding) to be at a certain value it gets hot to a point where you get heat for warming the room or making toast in a toaster (same principle) etc etc without actually melting Resistance wire - Wikipedia, the free encyclopedia

I am not sure of what the resistance used to be but it would take a lot of it to make a resistor up for what I need. But I did years ago make ballast resistors for the old points / coil types of car ignition circuits by winding old heater wire onto round mica core and then bury it in heat resistant ceramic cement in a ceramic moulded heatsink and then measure the resistance off as I went so getting the right value for that resistor - see pic for idea of what I mean bit I digress.... .:)

I'll go look for that Noctua fan again before i get carried away LOL!!

Just a thought John, is the cooler fan connector on the CPU_FAN header?

Britton30 said:

Just a thought John, is the cooler fan connector on the CPU_FAN header?

Yep Gary it is on the four pin header adjacent to the CPU (D) - in the pic I have the rear case fan plugged to the B header but in the text it says it is controlled I might just try it in that other header just off to the left and is marked as W

It says W is always on. Here are the resistors from a Noctua fan, odd thing is they are in the red wire, normally 5V and fans run on 12V. You can figure the resistance, I missed that class.

Ok Gary I'll try it in the red cable that is probably the answer thr CPU fan I have tried in the "B" header and it it now spins at 82 rpm!! I shall try the rear fan (140 mm) on the "A" header and see what happens as the diode temps have now risen FURTHER 2-3c which in all honesty is not a lot considering most of the airflow will now from front to back fans and the flow just sucked in by that slow spinning cooler fan.

Just thinking (that's dangerous) on a 3-wire fan connector the black would be ground, red hot 12V and yellow the PWM lead, for speed control.

In you link for Intel temps it mentioned some diodes will report a minimum temp even if the true temp is lower and then are accurate when above some threshold temp. I wonder if that's what is happening?
EX. the minimum threshold is 50C and the actual CPU temp is 34C, the temp will be shown as 50C anyway. When it rises above 50C the temp will be reported correctly.