The '85 has a bit of a unique system as it is the first year of the Klima relay. If the compressor doesn't start immediately, it's almost certainly a fault of the Klima. Either the Klima doesn't have the proper signals (unlikely because it goes into default and does not recover until the ignition is shutoff) or the Klima, itself, is not functioning properly.

What you observe is the traditional flaky behavior of the Klima.

I trust that you've confirmed that the compressor does not engage when you "don't get a/c". If not, then the aforementioned advice is not applicable.