It's important to understand that when you sync a module to a controller, the module is automatically unsynced from any controller to which it was previously synced. Some older firmware versions do support unsyncing the module from the controller; however, this is typically performed on the controller to reset the module address counter back down to A00.
Unsyncing the controller and module is commonly performed if a user wants to re-address his units with A00, A01, etc...Or, if the controller has reached the maximum number of synced devices. For example, in firmware version 5.0, this maximum is 200 devices, and once this limit is reached, Er 50 displays on the controller with all 18 red cue LEDs displaying.
The unsync process varies depending on the firmware version your controller and firing modules are running. Regardless of the firmware, when the devices are successfully unsynced, the SYNC LED will blink rapidly, and the controller will reset the address counter to A00.
Using firmware version 3.0.3, press and hold the module SYNC button on the 18R or 18R2 for 15 seconds to unsync the 18R2 from the module.
If using firmware 4.0.0, press and hold the 18R2 SYNC button 18R or 18R2 for 30 seconds, which will UNSYNC all modules from the controller.
Firmware 5.0.0 requires pressing and holding the channel up (CH +) and the channel down (CH -) buttons simultaneously on the 18R or 18R2 for 30 seconds.