Not sure about the temperature sensor.
With regards to the brake bias it is done through a brake bias valve (below the master cylinder fixed on the chassis, near the exhaust). Have you converted the vehicle to disk brakes? (if so... see my other post under the "splines" thread....) it may be of some use.
If it's an abs defender then brake bias is all done via the ABS controller...
the valve may be knackered or you have air in the system, but I've not come across this problem before so am just guessing.
Note, the valve only reduces the braking to the rear axle, if does nothing to the front axle (I think the valve because it is inclinded closes under hard braking (internals tip forward), thereby reducing rear braking, just a guess never taken one apart)
Rob