Heat through middle A/C Vent

[talljames]

Hi all, need to bring this issue up again as I did not find a solution.

Started experiencing heat coming out of one of the center vents while air con on with three blue dots on the middle wheel. I wouls start the car and after driving in hot weather and then stopping and starting at lights etc., heat would come out of that one vent. All the others were cold. Moved the wheel to three reds dots and it was a lot hotter.

While having the problem i checked the temp of the exit hoses from the heat control valves (the two on the side wall) and one was hot and the other very hot.

Had the gas topped up and found it was low as it had not been done for some years.

Problem reoccurred. I turned the a/c off and had the vents set for external air into the cabin. three of the vents were luke warm but that particular middle vent was hot. Turned the air con on again with 3 blue dots and checked the electric fan and that was working fine.

When the air con is on and i have three blue dots is coolent meant to enter the cabin from the heater control valves?

Hope this is not a bad blending flap.

Any comments much appreciated.