That's what I thought, but now the whole thing is working.
Had 24vac into the sending end of the control wires to the outside compressor,
20vac out when the receiving end was open-circuited
but zero when connected,
and zero current flow when connected. . .?
It was a bad wire nut connection outside that my HVAC guy made years ago. It came apart in my hand.
For these symptoms the connection must have been acting like a very high resistance.
I should measure the coil AC current while everything is still ticking.:yes: Getting contactor coil specs off the Internet seems pretty difficult.