15" - Late 2008 mbp. Past few months, fan speed almost continuously @ 6000 rpm, CPU usage completely normal. I've tried: - resetting Pram & SMC - Running hardware diagnosis (no errors) - Controlling speed with multiple applications (e.g. Fan Control) - even reinstalled OS It's driving me crazy. Does this really mean I need to spend 800+ on a new logic board for what looks like a tiny broken temperature sensor? Ideas / suggestions GREATLY appreciated!