Atlantic British recently put up an interesting video on replacing the blower motor resistor:
My blower is ok, but I feel the power is kind of weak, even on full blast. It seems like it should be stronger. Anyone think it'd be a good idea to replace this in an attempt to fix? The genuine part is a bit on the pricey side. Resistor - Climate Control Blower Motor (Genuine Part # JGN100011 ) - Land Rover connector\relays\flasher from Atlantic British

 

At full blast the resistor is bypassed completely. The blower has another known issue with the solder cracking inside the passenger fuse box/block. Typically the problem is intermittent power. Possibly you have a loss of amperage from this typical problem. I would try supplying direct 12v power to the blower and see if it performs better. Also, there may be trash inside impeding its performance.

 

I had same problem, and I pulled the blower motor and it was packed full of leaves. Now it blows like it should.