I have been having problems with the heater blower fan speed for a while now with only 2 speeds (i.e. dead slow or flat out with nothing in between regardless of any manual selection and I have tried the reset procedure with no success.
After reading a few posts here I was convinced that a new resistor was needed which is very expensive even secondhand but being a tightwad I thought I would try a simple fix.
Luckily I am a very skinny seven stone weakling so it is easy for me to scramble about in the passenger footwell and after removing the trim panel under the glove box I could just see the plug the fits in the resistor. It was a fiddle but I managed to touch the wires in the plug and give them a push as they felt a bit loose.
A quick test run and the fan is working perfectly on all five speeds again what a result for only five minutes work and no money spent!
If any one else has a problem with their heater fan speed this is worth trying, although if you have big hands you may have to remove the glovebox for access. It appears that the contacts in the plug can work loose over time, it is upside down which is not ideal.