I have 2 window units, both only 3 yrs old, 2 different brands. They were both operating fine last season. I just installed them and both 'light up', in that the temp default shows and the controls light up, but 3-5 seconds later, all lights go off and the systems will not start up. The fuse/reset has not been tripped. Hitting reset does nothing, but if I unplug the unit for 5-10 seconds, it will then do the same thing....on, then off. Can anyone suggest what the problem might be?? Wall power is fine, these are plugged into the same outlets they have been plugged into since purchase, circuit breakers are not tripping, but unit never actually starts up. The compressor never gets a chance to start. I never get the chance to set a temperature.

 

Welcome to the forums.

You could try posting the makes and models but it's pretty rare to have two completely different units do the same thing.

That could point to a power problem. Are these 120v or 240v units ?
If they are 240v units I'd check the voltage at the receptacles. If you were only getting 120v to them that would explain their behavior.