brake warning light

My brake warning light on the dash is on all the time. The service book for the military lightweight says check the servo. Brakes are working ok, but is there anything I can do to the servo anyway? Or could it be anything else?

Checked ya fluid levels?

fluids are ok. Could it be something to do with the dual system?

if its dual system theres a switch on brake valve on chassis drivers side under bulkhead,that supposed to tell you if either line fails probably faulty switch or short to it

To test the servo, pump the pedal several times, with the engine off, to get the vacuum out.
Then hold the pedal down firmly and then start the engine.
If the servo is doing its business, you can feel the pedal move down as the vacuum builds up.
Then stop the engine and pump again. You should get several pumps before it goes hard again.

If there's no change when you start/stop the engine, then the servo is not working: why it's not is another question.............

http://www.landroverweb.com/landrover/pdf-land-rover-manuals/
part 5 page 41

describes the complete brake warning system - you may have some or all of these components.

Thanks for all the advice so far - great! Downloaded all the manuals, just what I needed, and I'll have a go at the brake thingy next. Great site this!