Berlingo B9 van 59 plate heater problem

[Jackkeleher]

Hi guys 

B9 van 59 plate 

Heater works on number 2 but outputs the speed of 4 or nothing 
1-3-4 don’t work I changed the block relay under the glove box to no improvement 
I see a resistor block is available to buy but don’t n ow how to locate or if this would help

Any advice really appreciated

Thanks Jack