Fan problem

[MsPearly]

My fan will not spin so I decided to open the laptop to clean it from dust and replace the thermal paste (thinking that would be the problem).  But after doing so, the fan was still not spinning.  I take the laptop apart again and decide to see what could be the problem.  So, I took out the ram and HDD and the fan is running at full speed.  Now, I know that the fan does work but it just won't spin when I turn on the laptop normally.  I can not make any sense of this, so can someone please help me with this.

I have a HP Pro Book G1 450 Series

[Huffer]

This is a motherboard problem. Without memory the computer does not POST so you just have a direct electrical connection to the fan...straight power in. When the fan controller logic chip is activated at POST it is not telling the fan to turn on. 

[MsPearly]

I went through other forums to see if other people had the same problem and on one of the forums they suggested to check BIOS settings, to make sure fan is always running.  I went into the BIOS settings and the fan seems to be working now.  I've turned the laptop on and off a few times, and it seems to be running just fine now.  So, is this still a motherboard problem?

[Huffer]

I guess you never got it hot enough to need the fan. If the fan works with "fan always on" then the fan is working. If it never worked then it is a motherboard problem. We gotta work with the information you give us and you said it never works. 

[MsPearly]

I use the laptop for excessive gaming, so it gets really hot.  I used CoreTemp to check my temperatures, and it got up to 97 degrees Celsius.  And, yes, the fan did stop working, it wasn't spinning at all.  I don't know if it was because of the option or what not, but it just started working again.  I just decided to leave the option on because the fan seems to be working again, that was it.  So, that is why I wondered if it is was still a motherboard issue or not.  Like if something went faulty and decided to start working again?

[Huffer · Accepted solution]

Its not impossible. There are microscopic electrical chases in there and if the board is bent just right they can reconnect. I am still concerned the temperature sensor part of the fan controller may be bad. If it gets hot but the fan will not come on without "fan always on" selected in the BIOS then it might still be a motherboard problem. Battery life will take a big hit with "fan always on" but at least the laptop will not bake itself to death. 

[MsPearly]

Well, nonetheless, it is still good news to me.  So, thank you very much for the responses!