Only the blower speed is controlled by the sword. That means the fan speed. But not the temperature.
I assume that that the one side has a stuck heater valve. Maybe you just give it a wack with a plastic hammer.
You can also remove the plug on the heater valve block. If you look from the top of the valve (after you removed the black cover) there is on one side the wire loom with the plug (3 pins). When you remove this, valves should be fully open = heating.