The PSU should always run there might be a fault with the fan on the PSU, as far as i know there are very few which actually have fan controlling speed built in to the PSU, probably a fault, be careful with this as if the caps generate to much heat they might swell or pop, so dont use the machine until you have solved this. As for the chassis fan if you do not have any output ports on the board you might consider a molex adapter and connect the power adaption directly to the PSU current.