The backlighting of the switches on the Heat/A/C go out but come back on when you press the defrost button. Our 2000 Altima had the exact same problem. Since the Altima was still covered under the extended warranty we purchased through Carmax, we took it in and they determined it was a short in the control head. They replaced the socket assembly according to my itemized receipt. We never had it diagnosed or fixed on the Maxima.