I have a 250 watt PSU (FSP250-60HEN) supplying a GIGABYTE H55M-S2H motherboard with Intel Core i3 530 and a GTS 450 mounted on it, I don't have anything overclocked and most bios settings are on default.
Usually I leave the case open to keep the computer heat low and I don't mind clearing the dust every few weeks since it takes me 1 hour or so. Yesterday morning I had to move the pc to an other spot in the room and I leaved the case closed, in the evening while playing a videogame it shut down for critical temperature.
Today while checking what went wrong, I found out that the PSU fan was mounted facing upwards and as far as I know it's far better if it's face down, taking in cool air. After mounting it face down, at boot the fan started going "nuts", going almost at full speed and making a horrible sound as if the fan wings were touching a cable while spinning. I mounted it facing upwards again and the same thing happened.
The weird thing is, as I place the computer 90 degrees or so to the left it works perfectly. Since i cannot open the fan to check if something's wrong with it's engine, should I leave it like this or buy a replacement?