Here's an interview with the ad agency folks who built it:
Robert: There were a lot of calls with Clear Channel and Atomic Props to make sure that the board wouldn't weigh too much for the roof that it was mounted on, etc.
Steve: We used a prop house in the Midwest. They were great. I think we had to buy bulbs from 4 different lighting stores in the city to fill the damn thing. We wanted chaser lights but Coca-Cola was the last company to get that approved. It was weird because you can see the two boards at the same time. I think ours would have been better with chaser lights to really embrace the motel feel a bit more.
Robert: I do recall after a year or two that we had to get it all rewired. We didn't expect that it would be up for years. We were really thinking a year or two.
I always wondered if someone climbs up there to change the sign every week?
I miss the old Coke sign, but the new one is pretty cool. The first time I came to this city, the one thing I remember is that Coke sign. It was night. Bummer that it doesn't have a Diet Coke side any more.