The short story I'm looking for was published before 1990 but was more likely a 1950's to 70's publication. Machines of different classes and intelligence such as diggers and combine harvesters are confused without the presence of man. The machines speak to each other and end up fighting each other. A man ( possibly sick? ) arrives at the end. Thanks for any help
This is Who Can Replace a Man? by Brian Aldiss (also published as But Who Can Replace a Man?).
The machines, finding themselves with no humans to supervise them, set off to build their own civilization in the mountains. There they encounter a starving man who orders them to get him food - and they reply "Yes, Master, immediately!".
This is reminiscent of Roger Zelazny's For A Breath I Tarry..., an excellent short story about a post-apocalyptic world where Man is gone, and two great computers - Solcom and Divcom - fight between them about who is properly programmed to carry on the Great Reconstruction, as defined by Man before the fall.
I won't go into details about the end, and the eventual reemergence of Man, but I will say that the major character is Frost, an AI in charge of developement of the northern hemisphere, and his obsession with understanding Man.