Heater blows cold only in back of vehicle on 2004 Chevrolet Tahoe

I have a tohoe and the heat in the rear just stopped working out of nowhere now it just blows cold in the rear of the vehicle but the front heat works fine.
Do they run on seperate heater cores if so where do I locate the rear heater core?

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1 answer
I see a mode door actuator for the rear auxiliary air cond , temperature door and also a temperature control assembly available from the dealer or parts.com go to auxiliary air cond and click on auto temp control. Only way the heater core is bad is if it leaks.