1999 Honda Accord EX - A/c and Heating Panel Controls

Hi Folks,
I have a Honda Accord 1999 EX Model. I face a strange problem. When i
turn the car engine on usually the A/C and Heating panel light does not
turn on. I try pushing mode button, temprature knowb, a/c button
recirulation button but none of them have any effect and the lights do
not turn on. It seems as if there is no power in the panel. However,
The radio and cd player below it works fine.
After i have driven for 20 minutes or so, the A/C panel ligts
dramatically turn on and everything starts working great. These lights
may go out again at any time and it kinda keeps eaking out between ON
and Off stage at its own will.

I have not been able to establish a pattern of these lights/ system
turing on/off except that most of the time there is no light on the
heating and cooling panel. My car does not have an automatic Climate
Control System, so i ma discounting some setting issues in that.

When i took it to Car Mechanic, he was not too sure but suggested that
replacing the control unit right behind the Heating/Control Panel may
help as there was power in the main line when he checked it. But he is
not too sure.

If any of you have faced this issue, please let me know.

Regards
Ashish