Q: 10.6.3 fan not working

Try a SMC reset. The article covers when this is required, but doing this will not affect anything.

Reset SMC

If that doesn't work,

Reset NVRAM/PRAM

Try a SMC reset:

https://support.apple.com/en-us/HT201295

If no success, run an Apple Hardware Test:

https://support.apple.com/en-us/HT201257

Note that an error free AHT is not conclusive.

Ciao.