Computer Fan

The case fan in my computer was running slow. The computer is running hot. The original fan has three wires, I replaced it with a two wire fan and all is well. However I wonder what the third wire is for. The fan is 12v dc powered. Mike

Reply to
amdx
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The third wire is for speed control and monitoring. It allows the motherboard to vary the speed of the fan based on the systems heat.

Reply to
Tim Harig

That's what I thought, now I wonder if the motor is the problem causing the low speed or if the speed control (mobo) is the problem. Mike PS. I had three leaky capacitors near the CPU, I replaced 7 caps around the CPU and got the computer working. I suspect the fan has been slow for a while and the caps overheated.

Reply to
amdx

1 = GND/control 2 = +12 3 = tach pulse 4 = PWM

3 and 4 are optional, although 4-wire systems may not be happy if the tach line isn't present.

If your system supports it, the tach line can be read back through the (usually) SMBus and thus alert you if the fan fails.

Of course, as always, nothing prevents a mobo or fan manufacturer from using a non-standard pinout but the above is what pretty much all are using nowadays.

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Rich Webb     Norfolk, VA
Reply to
Rich Webb

That easy enough to prove ! Just disconnect the yellow wire. The fan will now try to run at full speed. If its still slow then its faulty !

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Best Regards:
                     Baron.
Reply to
Baron

It is often possible to clean and lubricate fans but it takes some work to remove the split washer that holds the motor shaft in place. Remove the fan label and the access cover that is hidden underneath the label. Immobilize the fan frame and look for the thin line in the washer. Using a small tool, carefully remove the washer taking care that it doesn't fly off to unseen places. These washers can also be brittle so be careful not to crack it into pieces.

Remove the shaft from the sleeve bearing or bearing chase and clean the shaft as well as the sleeve or chase. Re-lubricate using a light machine oil for a chase or a light grease for a sleeve bearing. Reassemble the parts.

The fan blades should rock clockwise and anti-clockwise when spun manually.

I've had some of these repairs add over three years to a fans life span.

Reply to
Lord Garth

Unlikely that the caps failed due to overheating. Replacing componentents on a MB is very risky. There are several layers between top and bottom, and its easy to screw up an internal layer.

Tom

Reply to
Tom Biasi

on

its

best approach is to stay away from the board; munch the component up with a pair of pliers until just the leads are left sticking out of the board, then solder the new component to them.

Reply to
z

Sounds like it would be good electically but ugly to look at.

Are there any photos of what this looks like on the web?

Reply to
Greegor

I don't know for sure, the caps are right next to the cpu heatsink, the bad fan is ducted to move air past these caps. The HP computer is about 5 years old. The old caps were Rubycon brand, replaced with same.

Maybe risky, but I had nothing to lose. I could have sent it to a pro and had caps replaced for about $75.00 or buy a new (different brand) board for about $60.00. I would have had to get drivers if I bought a new board. Sooo, If the board didn't work after I replaced the caps I would have bought a new mobo. The cap seller sent me 7 caps at no charge ( I don't know why) but I did send him $10.00 just cause he was so nice! It has been running 4 days continuously without a glitch, I think it's repaired.

A little history about the computer, I bought it used at 2 yrs old. Within

3 months I noticed a burning smell, I shut it down and opened it up. I found the power supply had a burned up power thermistor (
formatting link
) and carbonized area on the pcb. I cleaned up the board and installed a new thermistor. At the same time I found the power supply fan had a dead spot, if stopped on that spot it wouldn't restart. The manufacturer sent me a pulled fan, and I installed that. Now a couple years later I have the leaky caps causing lockup problems. Don't know if this is common for HP computers, but I don't have a good feeling about them now. Ya, I know, a 5 year old computer is ancient. :-) Hmm, I still have a 10yr old Abit KT7A 700Mhz PC running 24/7 without any problems. I just realized I still have a Compaq 100Mhz computer that is about 15yrs old, I think it's trash now, cause I stole the fan out of the Compaq for the HP. Maybe now I can part with it. Mike
Reply to
amdx

I cranked up the variable temp iron as high as it would go. Then made sure there was a little solder on the tip for good heat transfer, then applied heat to the joint until I could lift one side of the cap. I did the same for the other lead and then repeated until the cap was free. The caps did not come out easy, I started with a non variable temp Weller iron but that didn't seem to get it hot enough move the leads. I had to borrow a variable temp iron to get a little more heat. Once I had the caps out I used a stainless needle and the soldering iron to clean the solder out of the holes and allow the new cap leads to fit. Hmm, never used any solderwick or a solder sucker. The computer works fine now. Mike

Reply to
amdx

A hot air paint stripper is handy for preheating the mainboard before you try to remove the caps. It makes it easier on the soldering iron.

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Best Regards:
                     Baron.
Reply to
Baron

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