Krish,
This is a new one on me...and all of us I think ! I've never heard of anyone else
with this problem or anything like it !
Just a simple thought, have you tried gently pulling the control knob...
It may be that the control knob is broken....if it slides off easily.
Also...check out the Techie post on 'Changing the Heater Control Bulbs'...
http://forfour.co.uk/forum/index.php?topic=73.0Have a look at the 3rd picture down..... and you'll see there is a connector at
the rear of the heater control (in black), which connects to the heater valve.
Follow the instructions and get yours apart/dis-assembled like it is in the picture
and check it all out....to see if your connector/fitting has become detached, or
if it is broken in any way. Do look around and examine everything......not just
the obvious as you may miss what is the actual cause of the problem.
Let us know how you get on.
CrazyG