Car is stuck on defrost. Won't blow heat or air The two middle vents don't work. on 2003 Lexus GS430
A Lexus Scan tool and some professional grade scan tools have the capability to read trouble codes and carry out diagnostics on the heating/climate control on your car. The system uses servo motors, electronic control unit, and a controller. Hard to guess what wrong without being able to carry out tests on the system.