My 2 cents worth: I'm living in a late 50's house with 125 amp service. Frige, W/D, dishwasher have no noticable effect on the lights but I know exactly when the compressor in the garage starts. Since it is a 7.5 HP, single phase, line start, well I should. I think that dimming under normal household loads is a sign of problems. That is in the vintage of 2 wire romex, no ground, and very moderate electrical loads. Among other things, it is a prime candidate to have a FPE panel which, in itself, could explain the problems. Probably a good idea to have it checked out by somebody familiar with that kind of problem. If you're in the trade, get one of the old hands to show you the basics.
