THE COMPLETE SOLUTION - I had a similar problem on my 2002 Focus Ghia Estate, with only no. 4 position on heater blower working. The heater fan sometimes has had a squeaking noise like a leaf was caught in it or something, but not all the time. I took the advice here and replaced the resistor pack behind the glovebox. My local Ford dealer suggested buying the replacement plug in case it was burned out, which I did. Needless to say, the plug was fine on mine. After replacing the resistor, all 4 fan positions and the A/C worked fine. I returned the plug for a refund. After a couple of days the squeaky fan was noticeable again and then I found that only fan 4 position was working. Running the fan on max I noticed a fluctuation in fan speed coincidental with the squeaking. I sussed that the fan motor bearings were the problem and that the electrical overload had blown the resistor pack. This is most likely the cause in all cases, as on the resistor pack, below the green part which encases the resistors there is what appears to be a small resistor soldered between 2 terminals. This is in fact a sensitive, non-resetting thermal fuse. It is rated at 215 deg. C and this is what causes the pack to fail. I removed the fan and motor and found that the motor was stiff to turn. It is set in moulded rubber within the outer housing. By using a flat blade screwdriver to press down the rubber moulding tags the motor and moulding can be removed from the casing. The bottom bearing showed signs of rust but was not worn so I used some engine oil to lubricate it, making sure that it entered the bearing and wiping off all excess (do not allow oil into the motor or brushes!!) I used a long spout oil can to reach the bearing behind the fan too. After turning it rotated freely. The motor and moulded rubber were reinserted into the casing (use a little washing up liquid on the tags, and ensure they fully engage using a flat screwdriver). The fan assembly was plugged in while somebody held it tight as I ran it on the 4 setting. It rotated freely. Don’t just leave it on the floor of the car as it will jerk around when switched on!!! The fan assembly was replaced. Now for the resistor pack. I obtained a replacement thermal fuse from Maplin (228 deg C or 192 deg C as they do not do a 215C) for £0.79. I cut off the existing fuse which seems to be welded in place, not soldered, and using a soldering iron, tinned the terminals (and remaining fuse ends). The thermal fuse is sensitive to heat, so I used a pair of pointed pliers to hold close to the fuse to drain the heat as I soldered one end in place, then the other. I don’t know if the fuse is directional but I kept the cone shaped end on the same side as the original. After trimming off the excess wire from the ends of the fuse, the heater resistor pack was plugged in and worked perfectly. No need to spend £12 plus from Mr Ford on a new resistor pack when £0.79 will do !! My heater blower now works perfectly. I guess the bearing problem may return eventually, signalling the need to replace the fan/motor unit, but they are available on Ebay from £25 upwards (may have similar dodgy bearings), so possibly better from a scrap yard if you can examine it first. Otherwise new is £170 plus from main dealer.