internal fan heater works only on number 4(not 1,2,3)

Hi,can someone give me some advice, i have a 2 litre 206 hdi (2001),my
heater in the car only works on the highest speed but not a sausage on 1,2,3
speed. My fan must be ok as it works on 4,my mate is gonna have a go at
taking things apart and he aint a mechanic, so i need help.have you had this
problem.cheers joe

 

Speed dropping resistor or switch is knackered

Bob

 

rheostat blown
fast/full speed bypasses it

 

thanks for that ,is it a big job or can i do it myself with a Haynes manuel.
joe