Both Auto, Manuals, and PTs should be cleaned at least once a month. Items needed:
1 toothbrush
1 shot glass or small glass
1 small towel
1 bottle of Iso Alcohol 40%...90% is preferred...in a pinch hot water will work.
1 toothpick
1 sewing needle
Always unplug your PT before cleaning
Take either styled battery and hold the L.E.D. end up and battery down on the towel at a 45 degree angle. Pour some alchohol into a glass, dip the toothbrush in, scrub down the threads while turning the battery, then take the sewing needle and insert it into the air intake holes with circular motion.
Manual
batteries: Hold battery end down, dip the toothbrush into alcohol, use a circular motion around the battery post, the wipe down, and blow into the post area to remove excess alcohol.
Auto
batteries: Take a toothpick, dip into alcohol allow excess to drain off, then run it around the ring of the center post. This technique must be used since the Auto
batteries are not sealed and you want to avoid any liquid from entering the center of the battery connector post.
Blackened battery threads is a good tip that your batts need cleaning.
Hope this helps...