Heater temperatures are different side to side

More than likely you have an issue with one of the blend doors or the rod that connects them, or the actuator.

Here is a guide that shows how to replace the actuator on a different vehicle, but it is pretty standard.

https://www.2carpros.com/articles/replace-blend-door-motor

Take a look at the picture below and it will show the detail you need on this system. Even though you have a single zone temperature control, you still have two blend doors, they are just connected by a rod that will move both doors together based on the movement of the actuator shown below.

Again, I am sure you have an issue with one or both of these doors or the rod. I would access the actuator and move the doors manually and see if you have even heat. If not, then it is not the actuator.

Run through this and let us know if you have questions on this. Thanks

Okay. That picture is from a 2014 truck, so I assumed it was the same as they were the same DS classic trucks. However, they may have changed the design of it, but the idea is the same. There are two doors that are connected by a rod (internally or externally) and controlled by the single actuator.

So, if the actuator is fine then that is the issue. The reason they made these external in later years was because of this issue. They are just a little easier to get to when they are external like in the picture above. However, this rod is what needs to be looked at next.

Let us know what you find. Thanks