Pat, On my 09 ZR1 when I turn on the Air conditioning hot air comes out on the driver’s side and cold air on the passenger. any suggestions?

Sure do! There are several possibilities but the two most common that we experience here in the shop are control module and air blend door motor. The system uses various sensors outside and inside the car to tell the module what commands to send out to blend motors that control how hot or cold each side of the car will be.

As the sensors send signals the module which is actually a small computer analyzes them and decides based on internal programming how to set the air blend doors. Air blend doors control how much air passes through the heater core and how much air passes through the AC evaporator. Of course more air through the heater core means hotter air coming into the car and more air through the evaporator means colder air.

The air blend doors and on dual temp units there are two, one for each side of the car are moved by tiny electric motors. The motors have sensors that send signals back to the module so it knows when they have reached the commanded position. These motors often fail and when they do you wind up with a loss of control on one side of the system.

To avoid expensive testing up front turn the system single mode which can be done by turning the passenger side off. With the passenger side in the off position the driver’s side will control the temperature for both sides. By turning the temperature up and down you will be able to tell if both sides respond with proper temperature changes. If it continues to have hot on drivers and cold on passengers regardless of temp setting the side that doesn’t correlate to the set temperature has a bad control motor or parts related to the control motor.

If the temperature now works properly on both sides the issue is in the module or one of the sensors supplying signals to the module. In this case you will have to connect a scan tool to the car’s interface under the dash and look at the datastream information to see what signals are being generated.

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