The Volvo blower is known to crap out after about 20 years, pulling excess current and blowing the transistor pack (its actually not a resistor pack like Grandpas Volvo was)

If the resistor fails, three things can cause it: 1. rust rots through wire (not the issue is it is pristine when removed) 2. Blower air inlet is obstructed or the evaporator is plugged with debris. If it is these things then it would not have good air volume when on HIGH. The low airflow lets the t...