I have Dell Latitude C640. Its adapter works only when heated.
The LED light turns ON only when it gets extremely heated. I use to heat it on the electric heater.
Can anyone tell me the solution?
The solution is to by a new one, 9/10 the heat causes loose contacts to get connected. Anyway your adapter is broken, I don't really think you want a short on it when attached to your laptop, so replace it.