load of hot air

When I bought my jap 97 300tdi the previous told me that he had had the heater matrix replaced (reciepts supplied) and there have been no leaks,so all good,BUT......
...........whatever I do with the controls I get a flow of hot air down the spout into the drivers footwell.As I said,no water leaks.The rotary control appears,without being dismantled,to be connected as it clunks when turned quickly to the farthest extent.

Any ideas,gentles all?

The dampers controlling the airflow to the various outlets are operated by cables connected to the control knob next to the heater controls.
To get the symptoms you have normally means the cable has become detached from the damper or the control knob.
Bit fiddly but it is a case of finding the disconnected or loose cable. Could be at either end.

Kinda what I had thought,but since the rotary caused a clunk when turned I assumed (always dangerous!) that it couldnt be...thanks for the reply-I take it that there are several cables per rotary then?

Its many years since I had the interior part of a heating system apart and certainly never on a disco,so I know bugger all (makes a change then) about them.

shocksi