Duo-Therm AC not cooling
If the unit is a 220v, you will see 110v on that unplugged wire you mentioned. If it is 110v system then you probably have a swollen or open capacitor. The lil black box on the control board is a micro relay. And they do act up in different ways. If it's clicking, normally, that tells me its working. If it's 220v, make sure you have 220v to the system. If you have 220v to the system, and no power goilg through the micro relay, you can try jumping by that relay. While it's plugged into the relay (both wires), touch the 2 wire ends together with the end of a screwdriver for a second or 2 and listen for the comp to start. If it does you found your problem. All this does is bypass the relay by connecting those wire together. I've seen these units not work, if there is 2 units on the roof, due to a safety that doesn't allow both to operate at the same time, and never found the reason why. Now if it's 110v, you'll need to dig a bit more, following your voltage. Source, line, load. The source volts enter, the line feeds to the switch(s), the load is the motor/comp. The capacitor is a round/oval metal cylinder with wires attached, and stores voltage so it must be discharged by shorting the terminals to each other or ground. POWER OFF FIRST! Be safe please. If its 220v and you only have 110, check the breaker(s). If the capacitor is swollen up on top, where the wires connect, or have this sticky oil coming out of it, it's damaged. More that likely its the board. Last 1 changed was $129 my cost, not the customers. And I had to rewire the unit a bit and change the tstat also. So if you end up buying a board, ask them about an exact replacement. If it's not, ask them if they can draw you a schematic to help. Hope this helps!