I had exactly the same problem, and googled for hours to find the location of this resistor. However, I could not find find the solution. After much messing around I found the resistor in the drivers side footwell, high-up, next to the clutch pedal. It is positioned so high it is a real pain to get at. You can just about see it with the aid of a torch. It has 4 wires going to the connector. When you remove it you are really relying doing it on 'touch' rather than sight. It is retained using 2 torx screws. The bottom screw is fairly easy to remove, but the top screw is a sod as the clutch pedal rod is in the way. I managed to remove it using a 2" (50mm) socket extension, on the torx bit. As the torx screw is only screwed into plastic, it is not particularly tight.
In my case, the resistors were actually fine. It was the high power diode that was blown.
PLEASE NOTE: This is on a RHD, UK spec car.
Additional info: If you remove the resistor, position 4 still works on your heater control, but your air-con will no longer work.