Hello, I own a 2011 Hyundai Sonata GLS. Everything with the vehicle is fine until November of 2015. I noticed that the passenger side is blowing cold air when it should be blowing hot air. The driver side is fine. I thought it was a thermostat issue. At first I didn't change it until I noticed that the temperature gauge was acting up and realized that my thermostat was stuck open which made the engine over cooled. Once I replace the thermostat, I thought it would solve the issue with the passenger side blowing cold air but it did not. Basically its not a heater core issue, blend door is fine, the hoses that runs to and from the radiator to the firewall is fine and the one that runs to the water pump is good. Is anybody going through the situation I am going through. I closed the passenger vents so only the driver side blows hot air. Its an annoying problem. I know the dealer can fix it but they want an arm and leg and it seems like I may be forced to take it to get it fixed. May cost a few hundred to a thousand dollars which I want to avoid paying.