We just had our 4 year old Trane heat pump repaired, new expansion valve (TXV) and contactor (previous contactor was all burnt up... scorched). I noticed last night while in bed that our outside heat pump would come on for two-three minutes blowing warm air (80+ degrees at the master bedroom vents... T-Stat set to 68 degrees), then it shuts down. A few seconds later I see the blue/green Aux Heat light on the T-stat come on and the air coming out of the vents speeds up. I'll hear the heat pump outside come back on, but the air coming out of the vents is now droping like a rock from 80+ degrees down to 68-70 degrees. The Aux light stays on for at most 3-4 minutes then goes out. The outside heat pump is still running and I start to see the air temp reading at the register/vent rise from the 68-70 degrees back up to 80+ degrees until the T-Stat is satisfied and shuts off the heat pump. During the night I noticed this happening about ever 4th time the T-Stat would call for heat and the heat pump would come on. All the other times, it doesn't do it. Any ideas? Thanks.