Writing to those patient souls who still have a 252. First, a bit of background: Our 252 vents randomly from time to time, either the analyzer or the inlet, but not both. The power toggle switches were the first to consider, and they were cleaned with contact cleaner and actuated several times before receiving a clean bill of health. We have backup air pressure from a tank of medical air, as well as a UPS, so we can rule air pressure and power out. The FV pumps are all scrolls, which are working fine. So, too, are the turbos, no worries there. So, that leaves the vacuum safety system, of which I know next to nothing. I am suspecting the electronics for this system is getting old and I would like to override it. Has anyone attempted this? Anything I may have missed?