Wow! Im a few years late, but I have a recently acquired 3EE and I have similar issue... Ive checked grounds and wires and all looks and works great... however... i get weird ighting... the brew switches... when I am idle.. the light on right switch glows dimly, and if I activate any brew switch, the right light goes out and the left nad middle brew switches glow dimly... also when boiler refills, the same lighting issue.. left and middle light up, and right goes out... also.. when turning power to 1 ( no heat ) then the brew boiler light comes on dim... and of course one 2 the brew boiler light is bright as is should be... Im thinking it could have to do with fill box as I cant find any other issue...
Well I found my issue once talkign with LM ... apparently t switches were exactly backwards! and one was reversed ( the 2 blues on switches... ) its all solved! they all glow perfectly! not as bright as I thought they do in pics, but they glow and LM didn't refer to that being an issue... maybe its just how the swithes from EP are... anyway... its working great now!
Here are the wiring diagram, hope it can help.