Diag preformed on a carrier system Upon arrival client said system would run but cut off I checked clients filter it was dirty washed filter checked system red light LED was Flashing four times which means limit switch tripped four times reset system let system run inducer motor is making grinding sound but not over amping limit switch did not trip after filter was washed system is operational at this time ordering a box of 20x25x1 merv 13 shipping to client