Spoke with customer who informed me that compressor was making wierd sound in start up and shutting off. Checked capacitor which was weak. Put in a new one and ran system. While running the system it began pumping down. Verified airflow and everything is good. Suspected leak. Performed leak search with no findings. Ran system and put a pound of refrigerant in to see if pressures would change, the system continued to pump down until it shut off on low pressure control. Found troubleshooting manual from Trane and went through all flow charts. Temperature sensor checks are good, resistance on the coil is good, the EEV will open with the test open function and the suction pressure returns to normal and when testing to close the system pumps down as it should. The system needs a new expansion valve control board. Part quote request form has been filled out and estimates left.