I have inherited a commercial installation to maintain, installed by another company. The system is comprised of 15- 311 receivers, 4- DP34 switches, and one 18" dual LNB(119/110) dish. On a hilltop, no trees around. My BIG problem is, the receivers frequently intermittently fail. We find them with black screens, on channel 9600/9800, Dish500 screens, you name it. Sometimes we get a multi-dish switch failure message, where changing switch ports gets everything working. Normally resetting power restores operation, today operation returned after running a Check Switch, but it may have been because it was on channel 9XXX instead of 418. Usually 1-2 fail per week, sometimes more. Failure occurs in clear, rainy, & stormy weather. This rack of 3 per shelf produces much heat in an already hot room, so we installed 5 fans to help cool each group of 3 stacked receivers. We also added taller rubber feet for greater spacing. We installed UPSs to power the receivers to rule-out power problems. The signal levels are under 75% and that will be improved this week hopefully. Could heat be causing this? Are these receivers junk? Is it from low signal levels? To clarify, when the receivers fail, we always manage to get them going again. We have never swapped-out or replaced one. They have all failed at one time or another, and were returned to normal operation. Early on, the tech-support person walked us through different checks, and they ended up working -- we've never reached the point where they suggested replacement. Any suggestions appreciated.