How can I connect a humidifier to a Goodman dual fuel heating system?
According to the Installation Instructions for a Goodman GMVC95, there should be a 5&quot; brown wire hanging around, not a terminal.

24 Volt Humidifier
A 5&quot; long brown wire in the wire harness at the low fire pressure switch provides 24 VAC humidifier control. This wire is powered any time the pressure switch is closed. To connect 24 VAC HUM, connect the 24 VAC line of the humidifier to the 5&quot; brown wire. The connection can be made by either stripping the wire and using a wire nut or by using a field supplied quick connect terminal. The wiring must conform to all local and national codes. Connect the COM side of the humidifier to the C terminal on the furnace control board (or to the COM side of the 24 VAC transformer). Do not connect 115V humidifier to these terminals.