you stated:
Some may not understand what that means, so I thought I’d explain / illustrate.
The flyback diode is connected in reverse polarity to the supply voltage. In other words, the cathode side of the diode is connected to 24+ and the anode side of the diode is connected to ground. see illustration at the bottom of this post and note the reverse polarity
A diode’s schematic symbol and “physical anatomy” are represented here:
The reason a diode is important has to do with the magnetic coil of a mechanical relay. In simple terms, the moment the controller stops sending 24v out, the coil of your solenoid or relay returns current in the opposite direction towards ground and the diode provides a path (a loop) for it to “freewheel” back through the relay coil with minimal resistance (keeping the voltage from spiking dangerously).
@BobAbbott, unless you are sure that solenoid has a diode, it is cheap insurance to add one. You can test if a diode exists simply by connecting a 12v LED (in reverse polarity) to the controller’s 24+ and Wind - terminal. When wind shuts off (closes), if the LED blinks then your solenoid does not have a snubber diode.
You could add one like this:
Or… use a Solid State Relay (SSR) 