Why would replacing the thermal compound make this sort of difference? Is there a sensor that would be affected by that?
It shouldn't. TIM (thermal interface material) does not "go bad", dry out, wear out, get old or need regular replacing AS LONG AS
the cured bond between the mating surfaces is never broken. The exposed edges may dry and get a little crusty, but the TIM between the mating surfaces will remain viable for 10+ years or more - if not undisturbed.
If the computer has never been bounced off the floor, the heatsink never removed or otherwise disturbed enough to break the cured bond, and the heatsink mounting mechanism is still properly attached, you don't need to replace the TIM.
You MUST however, always thoroughly clean the mating surfaces and replace the TIM whenever you disturb or remove the heatsink once is has cured (and note the curing process starts the very first time heat is applied).
Did you remove the CPU
's heatsink? If you did, did you thoroughly clean the surfaces and apply a fresh new, and proper
(thin as possible but still complete coverage) layer of TIM?
The most efficient transfer of heat occurs ONLY WITH direct metal to metal contact. The sole purpose of TIM is to displace any insulating air trapped in the microscopic pits and valleys of the mating surfaces. Any excess TIM is in the way of direct metal to metal contact and therefore counterproductive to the most efficient transfer of heat.
's sensor is located on the die (inside the CPU
housing) so there is no way it can be affected by TIM.
I agree with Tony and suggest you look in the BIOS
Setup Menu for threshold temperatures and perhaps fan control settings. Something may be off there.
Alternatively, you may need to "Mickey Mouse" this a bit and power the fan directly from a power source instead of the fan controller - if the system allows it (some systems will shut down if no fan is detected even if not hot).