Elitedesk 800 65W G2 Secondary fan

[Stuart264]

I have an issue with an Elitedesk 800 65W G2 where the secondary fan is not increasing in speed when the processor(s) hit 100% and it's overheating and doing a forced shutdown.

I suspect it may be an issue with the thermal sensor as the fan works fine and the system stays stable if I override the fan speed to 100% in the bios (it does sound like a jet engine though)

Could anyone advise on 2 points?

1. What's the best way of obtaining the readings from the thermal sensor so I can check if it's actually the cause of the fault?

2. Is that part still available as I have seen some second-hand parts available but no new ones.

TIA Stuart.

[DGroves]

 the elitedesk 800 G2 SFF was released in 2015 and is out of HP's warranty  (same for the tower model)

checking/replacing a failing/failed fan yourself  is not that hard for most end users to do, a quick check is to try spinning the fan blades by hand and noting if it spins freely, if not read the fans label for the model number and do a google search for venders selling that model

just because a cpu hits it's throttling temp, and increases the cpu fan speed does not mean that the case fan will also increase fan speed

 generally the case temp needs to rise above the sensor preset value before it will increase the case fan speed and it will take time before the increase in the cpu cooler's exhaust air will increase the case temp

however some small form factor motherboards unlike full sized motherboards will have sensor settings that does increase both the cpu and case fan  (if equipped) at the same time

the Elitedesk 800 65W G2 motherboard ramps cpu fan speed and case fan speeds separately depending on each fans sensor values

if you have the SFF model, if might be that the issue is the CPU/cpu fan rather than the case fan 

increasing the case fan to 100%  will will cool the cpu if the cpu cooler itself has a problem

[Stuart264]

It's not the fans, both test out fine, but there is no "ramping" as the processor hits full load, Speedfan reports core temperatures of around 70C at full load. I suspect I will have to dig around for a replacement thermal sensor and try that.