Watch the wiring
No doubt you already took care of this, but, prior to the blessed days of central AC, when I installed the first window ACs in my townhouse (one in the living room and one in the bedroom upstairs), I plugged it into the wall outlet and ran it. Apparently the wires were taking a little too much load. The AC quit one day, and when I opened the plug to see what the problem was (after checking circuit breakers), the wires had corroded away to nothing and broke. I still have no idea why no smoke or fire happened, or why the circuit breakers never snapped.
Hired a really-for-real electrician who ran dedicated high-amp circuits down to the AC locations. No problems after that.