If it says AC, but the controller itself has a DC label, then something is damaged — the firmware uses the information stored in a EEPROM on the controller to detect whether it’s AC or DC. If that chip is damaged, it won’t be able to read the DC information, and by default it will treat it as AC.
You mentioned using a 24VAC transformer — are you aware that you should NEVER plug in a 24VAC transformer to a DC powered controller? The DC-powered controller only accepts DC power adapter, up to 12VDC. A 24VAC transformer will fry some components in the controller for sure.