Why Is My 2005 Acura RL Heater Blowing Cold Air on the Driver's Side?

If your 2005 Acura RL is blowing cold air on the driver's side while the passenger side is warm, the likely culprit is the blend door actuator. Many vehicles, especially those with dual climate controls, have two actuators that regulate the temperature on each side. If one of these actuators fails, it can prevent the temperature from being adjusted properly, resulting in one side blowing hot and the other cold. You mentioned that the air conditioning works fine, which further points to the blend door actuator as the issue. The strange reading of 112.5% during the self-diagnostic also suggests a malfunction in that component. To access the actuator, you'll need to remove the panel below the glovebox on the passenger side. This should be covered in the video I shared, but if you need written directions, I can help find those as well. While waiting for a new actuator, which typically costs around $130, there isn't a straightforward way to manually set it to blow warm air without risking damage to the unit. Attempting to adjust it manually could potentially break the actuator altogether. If you decide to proceed with the replacement, just take your time and follow the instructions carefully. If you have any more questions or need further assistance, feel free to reach out.