PS3 Fat Cechc Loud Fan even after new Thermalpaste and dust cleaning

Hi, for some time i wanted to play some old games for the PS2 (Ratchet & Clank), but my old PS2 is broken. So i tought i buy a used PS3 with backwards compatibility. So that i dont have to pay 40 Euro shipping and taxes i bought and PS3 Fat CECHC04 on ebay. The seller mention that ther console turns of after 5 min and the Fan spins at full speed. So i bought this unit, cleaned it and replaced the old thermalpaste. But even after this the Fan spins at Fullspeed. Could it be a faulty fan, broken thermalsensor or some other problem? Please Help.

Update, a new Fan and fully formating the console didn’t helped.

Another Update, i found a post an another Forum and after i followed the steps it doesn`t Spin at Fullspeed. Here the post: „psx-place. com/ threads/ 23066/„