Capacitors are not being utilized after 5 minutes of operation.The run capacitor is in play whenever the air conditioner is running, and a bad run capacitor could very well cause this exact failure. Since there are several other possible causes of this exact failure, I'm still of the opinion that isolating to the generator or the load via measurements is the logical first step. But if the OP just wants to try something, Chris' suggestion of cleaning the air conditioner is a good thing to do anyway and is backed by a lot of actual experience.
