Went on a service call last week that the homeowners were complaining about the upstairs H.P. was running continuously even with the t-stat in the off position. This is a 2 system house with a 1.5 ton upstairs and a 2.5 ton downstairs. When I first got there i noticed that the installers had the 2 heat pumps backwards ( 2.5 ton H.P. on 1.5 ton air handler and vice versa). So the first thing I did was switch the units around. after getting both units up and running both units operated right like they should never getting either unit to run with t-stat in off position like homeowner had stated. Even replaced t-stat upstairs and redid low voltage on the upstairs unit thinking that there might be a short in them which would cause this unit to run all the time. They call back 3 days later saying the unit had started doing the same thing, which is know the downstair H.P. I hope and think that we can assume that the problem is within the H.P. itself. Going back tommorrow to see what I can do, Any suggestions?