Has this ever happened to anyone else other than me? You go on a commercial office building inspection. You adjust the stats to check the operation of the heating and cooling. After changing the belts and filters of course,You check operation of all rtu' and ahu's. Eveything works fine. You set all the stats back to their orginal place. Next day a service call comes in. "Our heat and or cool doesn't work". You go and check it out and find some bad stats and a bad evap. motor. Keep in mind they worked yesterday(honest). You explain to the customer and eventually your boss what happened. They both say "you were just here yesterday". What can you say? It's like, just by working the stats and equipment it broke it to work in auto mode! It seams like that this happens to me at least once a year. How in the world can I prevent this from happening?