2004 Pace Arrow battery drain

I bought an 04 Pace Arrow new and have never had battery charging problems until this year, when plugged in to shore power you hear a clicking sound about every 30 seconds coming from the fuse box area under the hood, and the batteries were not getting charged, a local dealer replaced the auxiliary start relay, and that seemed to fix the problem for about 2 weeks, today the 12 volt battery was dead, and the clicking sound is back, I was able to start the generator so the 2 six volt batteries are charged. has anyone had this problem ? I will take it back to the dealer tomorrow. Workhorse chassis, 8.0 liter

Thanks