Ordered needed hinges plus replaced the top hinge and spring while I was at it. Used previous repair stories to get instructions. No one else mentioned replacing the cover, ie middle hinge so that was tougher. Couldn't remove the cap under the middle hinge but was able to pull out the old one and insert the new one by carefully twisting it in. Must unplug the cable first. Mullion works great now.
Parts delivered in one day - wow!