Dell 8200 shut down

[computeit]

I have a Dell Dimension 8200 that is 3-1/2 years old. About a month ago, it started shutting down after about one day of operation. It started up okay and the log showed that each shut down was due to the CPU fan. I replaced the CPU fan with exactly the same fan, but it did not solve the shut-down problem. Does anyone have a suggestion? Could it be a software problem? Dell support could not offer a reason for the periodic shutdowns except for a possible malfunctioning CPU fan. Thank you for your help.
Otherwise, I have had no problems with the Dell 8200.
Computeit

[spyder913]

make sure your heat sink is actually transferring heat away from the CPU, you may need to reseat it and add some thermal paste.

[computeit]

Here are three more facts about my problem:
1. When I look at the CPU fan at the back of the tower when the computer is running, the fan is not spinning.
2. After the computer shuts down, the log says "Out of Range CPUO Fan.
If I am working on the computer when it shuts down and I start it up again, the computer does not shut down again soon after but may continue running for hours before it shuts down again.
3. An inspection of the inside hardware of the tower does not seem to show any heat damage, and the computer runs well before a shut down.
computeit

[Rooster]

Definitely heat.
I don't see how you're not getting shut down quickly after bootup if your CPU fan isn't spinning.

When you say your CPU fan isnt spinning - are you referring to the rear case fan?

In a Dell - I believe that is one and the same (I just want to make sure). It has a green plastic duct that runs from the rear 80mm fan over the heatsink on the CPU correct?

[computeit]

Yes, the fan serves both the case and the CPU and is encased in a green housing. Even when the computer is booted up after being shut down for 8-10 hours, the CPU fan does not start spinning. The computer may stay on for hours, without the fan spinning, before shutting down. Thank you for your help.

[Rooster]

It really depends on ambient temperature. the power supply can help create an airflow from front fan to power supply, passing by the CPU - cooling it enough.

Try replacing with a different fan (with a 4 pin molex adapter).

[computeit]

Thanks for all the help and suggestions I received. I finally determined that the CPU (case) fan connecton on the motherboard was not delivering power to the fan. Therefore the alternative was to connect the fan to the power supply. Since the Dell fan did not have a molex connector and I had two other fans that did have molex connectors, I daisy-chained them and connected them to the power supply. The computer is working now, but it is too soon to know if it will shut down again. I am concerned that I now do not have use of the third-wire sensor that comes with the Dell fan. Also, I now do not have the green plastic fan shroud installed. Will this arrangement work OK or should I put a molex connector on the Dell fan and use it with the shroud instead?

[Syri]

I'd get the dell fan working, as the shroud is designed to channel the flow of air. It will still work a bit without the shroud, but nowhere near as efficient. The only difference not having the fan speed monitor will make is that it will run full pelt all the time, instead of slowing down when it doesn't need the full speed. in other words, will keep it nice and cool, just might be a bit more noisy when it's idle.
I have a dell as a second pc myself though, and if your fan is even twice as loud as this one at full, it won't be noticable anyway, mine's really quiet running even under load.