Expansion Valve: Description and Operation

A defective expansion valve could cause insufficient air conditioner performance on the one hand and damage to the compressor on the other hand.
If the expansion valve is metering insufficient refrigerant into the evaporator, the air conditioner performance will be reduced since only part of the evaporator will be used.
If the valve permits too much refrigerant to enter the evaporator, the compressor could be destroyed by hydraulic lock.
The expansion valve is adjusted during manufacture for maximum performance and this adjustment must not be changed.