These are ungrounded AC circuits so there isn't really a positive or negative side of anything. And I don't follow the comment about no reading on your meter. What is it you're trying to measure?
As far as the A relay is concerned, it should fire whenever any of the other relays in series with it fires (1B, 2B, 3B, 4B or 5B). Assuming the 1B,...,5B relays can fire that indicates that the A relay isn't open (ie. it doesn't have a broken wire in one of the turns). What happens sometimes though is that these relay coils are replaced with the wrong coil of the same size. The 1B,...,4B relays should all have A-1119 coils and the A relay should have an A-9746 coil.