Air conditioner for vehicle and method for controlling the same

A method for controlling an air conditioner for a vehicle including a PTC heater comprising the steps of:

• comparing a target discharge temperature of a first air passageway with a target discharge temperature of a second air passageway with a control unit;
• reducing a PTC heater output associated with one of the first and second air passageways with a lower target discharge temperature by an amount associated with a compensation value in order to prevent an actual discharge temperature from one of the air passageways from becoming higher than the target discharge temperature of the one of the air passageways as heat from one of the air passageways with a higher target discharge temperature is conducted to an air passageway with a lower target discharge temperature if the target discharge temperature of the first air passageway and the target discharge temperature of the second air passageway are different from one another, wherein the compensation value is set to be proportional to an absolute value of a difference between the target discharge temperature of the first air passageway and the target discharge temperature of the second air passageway;
• establishing one of the first and second air passageways having a target discharge temperature that is lower than the target discharge temperature of the other of the first and second air passageways as a lower target temperature zone, and comparing an actual discharge temperature of the lower target temperature zone with a target discharge temperature of the lower target temperature zone minus the compensation value, if the target discharge temperature of the first air passageway and the target discharge temperature of the second air passageway are different from each other;
• and
• reducing the PTC heater output associated with the lower temperature zone by an amount associated with the compensation value if the target discharge temperature of the lower target temperature zone minus the compensation value is less than the actual discharge temperature of the lower target temperature zone.