Land Rover Repair: Brown outs on electrical system, water ingress, high beams

Question
I have a 99 Disco II and while bringing the vehicle up to speed from a stop the electrical system has quick but noticeable brown out. The raido will reset and the lights will glitch and the system will recover.  This also happens if I turm on the high beams or anything else that may draw a sudden load from the electrical system.  I have replaced the alternator and the battery to no avail as well as cleaning all the grounding systems that I could find. This happpens about 10% of the time from take off.  This is the model that comes with the Warn winch as well as the Hella lights mounted on top.  Any ideas what this may be?

Answer
Any model equipped with off-road equipment has the possibilty of water ingress, which will cause damage to the fusebox in the engine compartment.  I have seen this a number of times.  Also the multi-function unit in the passenger compartment fuse box occasionally goes bad.

I would also recommend that you double check all grounds and battery positive connections.