Just saw your post here, 1 part white vinegar, 1 part household ammonia, 2 parts distilled water. I would run it 30 minutes and if the light was still on would change out the solution and run it again, when clean it will be out or barely visible. Be sure red+ is hooked to the barrel and black- to the rod. I got this info off the internet quite a few years ago 10-15, built it and have used it on several of my milsurps and several friends, everyone satisfied. Google may find it for you?