We recently shut down our server to replace the batteries on its UPS. Normally, the fan runs on high when it is first booted up and then returns to low (or off) and is essentially noiseless. Since we replaced the UPS batteries, the fan stays on continuously and is quite noisy. I shut it down and plugged the computer into the wall outlet with the same results so I think I can disqualify the UPS as a problem, i.e., in the event it was getting inadequate power. I'm trying to figure out how the fan is controlled with the idea that perhaps something was reset during the battery replacement. However, I don't have a clue. Any ideas? Assistance is much appreciated.