Thank you Steve, those diagrams help. I have one of the original capacitors, the one that smoked up the house. AD apparently is the brand, 15 mfd (±10%), 370v.
There's an unlableled component that the compressor common goes to. Maybe a relay. Doesn't look like one to me, but this rectilinear capacitor could have fooled me if it wasn't labeled.
I bought a pair (I like spares) of CSC 15 mfd (±6%) 370v. from McMaster-Carr. I'll try using both. I wasn't aware dual was a possibility. Only 1 line voltage into the original capacitor, with two wires going out to the compressor, labeled S and R on the wiring diagram.
Difficult to figure out when you don't know what's required to make something work.
I was guessing the first diagram in that link was correct, but it didn't work. Of course I also don't know if this compressor is going to work. It was never used, just sat for close to 20 years.
You've been around YT since 2013, wouldn't remember T_Bone? I had a problem with a mismatch between the HPWH and my electronic controlled tank heater. The Whirlpool and Crispaire techs conferred and said they wouldn't work together. T_Bone helped me work it out, how I became friends with him. Amazing what expertise one can find on these boards.