UPDATE: I eventually got T_Sensor working at some point while hard-resetting CMOS and re-flashing the BIOS.

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The T_Sensor external temperature sensor doesn't seem to be working on my motherboard. Can anyone confirm whether this is just my board or more a wide-spread problem? From past experience my guess is this is probably a ASUS EC / BIOS problem on all Z370 boards.

Originally the sensor included with the Z370-E motherboard was zip-tied hanging in the case monitoring ambient temperature got a reading of 29.8C. Since this seemed to be a reasonable reading, I assumed it was working.

While overclocking, I began to see 'Motherboard VR Thermal Throttling=Yes' in IXTU. I verified that the VRM heatsinks were getting too hot with an infared thermometer. Under load they are nearing 100C in places on the outside of the heatsink with semi-good airflow so the VRMs themselves must be quite a bit hotter. This is a water cooled system, so it might not be getting really good airflow over the VRM heatsinks.

To address this issue, I added a 120mm fan (powered by rear exhaust fan via Y cable) to blow over the VRMs, taped the T_Sensor probe between the fins of one of the VRM heatsinks, and in the BIOS set the rear exhaust fan (and VRM fan connected via Y cable) to throttle up as temperature rises. The problem is that this had no effect on fan speed.

Investigating, I found that the output of T_Sensor will not change from that 29.8C reading no matter what, load or idle. I assume this isn't a software / driver issue since I get the same 29.8C reading in the BIOS and in Windows.

Suspecting this may be a defective thermal probe, I replaced it with an aftermarket unit (XSPC Wire Sensor 10K) and taped it down to the heatsink with foam tape to make sure it's getting an accurate reading but I get the same exact 29.8C reading even though the infared thermometer reads 80-90C nearby on the heatsink.

(By the way, what ever happened to the VRM_Temp sensor that was built into the motherboard in the Z170 and Z270 series boards?)

Currently I'm working around the problem by using CPU temp to throttle the fans, but this is annoying because it throttles the fans too aggressively. This DOES fix the VR Thermal Throttling issue, but I'd really like these fans to spin up only when the VRMs start getting hot.

Either I'm doing something wrong, this is this an ASUS EC / BIOS issue or is my motherboard defective?