Cool and hot air problems 1989 300E

1989 300E. When using the temp controls the heat works excellent but when inside of the car gets to hot I like to turn the heat down but the temp inside of the car does not change. The cool air does not kick in only hot. When I turn the hot air completly off and but only cold air on the hot ait is still there, no cold.

Help please

Thanks

Fab

[joel]

check the air sensor at the dome light. i bet it is clogged.

I checked the sensor on the dome light and it is clean. Is there anything else that could be causing this problem?

Thanks