I updated an old Interactive system to a wired QS system which worked fine for about six weeks. Then, my client calls and tells me his keypads (all 12) had stopped working for about 18 hours then were fine. It happened again over most of the weekend but again worked fine on Sunday night. I stop by on Monday morning and they are working. I check the voltage and its 23.9v. and leave. Two hours later they are dead again - I come back later that day and they are again working normally. Has anyone had any experience with this?