heater/blower?

Hi guys thought i had my heater blower fixed last friday .garage got me new resistor pack and fitted it,great thought me,nice warm car on friday and saturday,then havnt used car again until today. started car ,and lo and behold heater not working at all again.!!!!!! spoken to garage who are going to test the part they fitted and check fuse,does anyone out there know or can think of any other reason for it to stop again,other than a faulty resistor pack that was fitted?? garage say its not the blower motor as it is fitted after the resistor so any clues?