I'm about to start building a PC, so far I only have my PSU and case, so to check if they were working, I plugged a built in case fan to the PSU, then plugged the PSU in and turned it on, the red power light came on on the PSU, but neither PSU fan spinned, and nor did the case fan i'd plugged in. Is this just because i've not connected everything else like the MoBo and stuff, and is this normal for a PSU?