Mine used to overheat when driving for more than an hour with the heating on. With the fan installed, it has never gone over 46°C (on a 2 hour drive with the heating on as it was freezing cold). When I had the fan installed, I set the alarm at 40°C and raised it 1° each time the alarm went off. It stopped triggering at 45°C. Only during that 2 hour drive did it reach 46°. It hasn't triggered since. I do have to add that the heating ducts don't blow hot air directly on the empeg. The radio is in between. FWIW.

Frank