|Checked the FAN...how?|
Could be simple as dirty exhaust vents and fan inside the unit. Or could be a motherboard sensor on the fritz controlling a fan.
I just ripped apart an HP Pavillion Dv4 laptop. The fan was continuously running on high and unit was shutting down. I thought it may have been a motherboard issue, but there was a large dust bunny stuck in the exhaust vent, and another one stuck on the outside of the fan. I blew it all out, thermal pasted up the CPU heat sink, reassembled it...it's purring like a kitten.
MOOOOooove! OH and you're welcome!