I have an ibm thinkpad T42 notebook, when i turn on the power button I got a black screen, the power turns on the power light, battery light, and the z light, no hard drive light, and on the screen nothing comes on, not even a fun error message or the post bios test, all is black and blank.

Possible memory failure.
Try removing memory modules one by one and test the laptop with each module separately. Try using different slots. One of the memory modules could be bad.

I have the exact same problem. My T43p with new fan will power on but after 15 seconds it shuts off without warning. No error, no over heating, just shuts off.

So I put back my old fan without thermal grease and it works. It seems the my new fan, I purchased a refurbished one from e-bay, has some issues.

I have t43p. It had a noisy fan so I took apart the laptop to try to clean it (I did have the glued / stuck thermal grease issue as mentioned elsewhere here, but a firm hands got it off). When I reassembled I started to get “fan error”. Thus, upon startup, the fan pulses, starts then stops then starts again etc never really getting going and a couple of seconds later the fan error message comes up and the pc shuts down.

Not sure what’s going on. Did you apply thermal grease on the CPU before installing the heat sink?

I replaced the fan in my T42, and it seems to be working (the fan), but now the computer shuts off after 10 seconds when I turn it on. This happens when I reconnect the old dysfunctional fan as well now (I pass the fan error by blowing air with my mouth and the fan spins for a few seconds). It doesn’t matter what I do at startup – within 10 seconds it will shut down.

Did you replace the entire cooling module (heat sink and fan)?
Did you apply thermal grease on the CPU?
Did you notice if your new cooling module had thermal pad for another chip?

It’s possible that your laptop shuts down because of overheating. Make sure that thermal grease is applied correctly.

THANKS!

Its kind of hard for me to describe, but my laptop seems to be different than the maintenance manual and the picture above. Mine looks like the picture above but what you call the “fan assembly” is connected to that heat sink on the right of it (grey with blue center). This is connected to the mother board by some type of hardened glue or solder. Making the fan assembly and heat synch all one piece and un removeable.

Here’s a list of manuals for IBM/Lenovo laptops: http://www-307.ibm.com/pc/support/site.wss/MIGR-39298.html.
Find your model and look in the service manual. Maybe you can find help in there.