System Thermal Sensor Location?

I have a new GA-EP45T-DS3R (rev. 1.0) and I can't locate the
motherboard/system thermal sensor.
The Motherboard/System thermal sensor shows an idle reading of 42C with the
case sides off, higher than any of the other sensors. If I stress test the
PC this actually drops to 35C, presumably because I've got my front case fan
paralleled with the CPU fan which revs up under load, cooling the sensor.
Anyway, the high reading is daft. I was thinking it might be more useful
with a small heatsink attached.
Does anyone know exactly where the sensor is? Has anyone tried improving its
function?
Thanks,

Scrim