Resistance checks on both compressors came in about the same. Common to Run, 10 and 11 Ω. Common to Start both 10 Ω. Start to Run 12 and 16 Ω.
Compressor frame to each wire on both compressors was infinite.
Using a headlamp I did see that the block in the diagram to the left of the compressor capacitor (COMP C), that the compressor common goes to, is indeed a relay. The diagram doesn't tell me anything about what it does, but there is a diagram cast into the plastic housing if that would help anybody.