I just wanted to add, most controllers have diagrams published either on their website or on a venders. Not anymore complex than finding the controller brand and part number. Don't forget when troubleshooting Chinese equipment the equipment Ground is not always 100% connected to the machine. So if its 240 volts check line to line not to ground. If its a 120 volts, LN or Hot to Neutral or grounded conductor. I taught the same thing I posted above, a visual check for loose or burnt wires will find a lot of issues. We used the KISS rule, and always do the simple stuff first. Power and then visual.
Retired Guy- Central Iowa.HVAC/R , Cloudray Galvo Fiber , -Windows 10