I have had my Infinity system with a Carrier 38TDB-060310 two speed compressor. about two years. It ran fine at first but in the last year it has started making a lot of noise/vibration when cooling. Not all the time but about in the middle of the cooling cycle. When the technician comes to check , it never wants to display this noise as he comes in the day for a half hour and is never here when it makes this loud noise, which is much worse at night. Supposedly the two speed unit reverses rotation when going from high to low and is supposed to stop about a minute while doing this reversal (I suppose to let pressures settle). I never hear the unit stop after it starts cooling, it cools a while,running very quiet, then all of a sudden starts making a lot of noise and vibration, then after a several minutes starts running quiet again., then shuts off I guess when the thermostat says to. Could it be that the compressor not stopping cause this very bad "harmonic" type noise and vibration? Or what could it be. Thanks