If the heater fan only works on position 4 and not 1,2 or 3 its the resistor unit that needs replacing.
1) remove the felt lining underneath the glove box (4 screw clips) & resistor unit can been seen fixed to bulkhead to right of fan
View attachment 18627
2) remove phillips head screw and pull out resistor unit. Disconnect electrical multiblock
View attachment 18628
3 fit the new one (got mine off ebay approx £8) and fit lining back
Hopefully someone might find this useful
1) remove the felt lining underneath the glove box (4 screw clips) & resistor unit can been seen fixed to bulkhead to right of fan
View attachment 18627
2) remove phillips head screw and pull out resistor unit. Disconnect electrical multiblock
View attachment 18628
3 fit the new one (got mine off ebay approx £8) and fit lining back
Hopefully someone might find this useful