Recently upgraded an optiplex 7010 sff system for someone, temperature and stress tested and everything was fine. However a few weeks later they're having problems with a "rear fan failure" error message happening on boot. It only happens some of the time, and causes the fan to not run when it occurs. Could this be a bios issue? They live quite far away so I'm trying to figure out what to reccomened they check just incase it's a simple issue, before I get them to bring it all the way back for me to fix. In particular I'm wondering where the connections for this fan are as i don't think they'd be comfortable taking too much apart to get to them. Any advice would be greatly appreciated, cheers.