N4050, Plug in not charging issue.

It's N4050 dual core (B950 chipset). When I plug in my charger it says "plug in not charging" but if I insert the charger pin and quickly rub the laptop bottom (left side or fan side) on a cloth-surface (sofa etc) it starts charging. I've changed the charger but it didn't work rather my charger works perfectly on others. I've also changed the batteries but the the problem remains. My system is well maintained (am not a beginner) and everything goes fine in tests. Am using Windows 8.1 32bit (own purchased).