Ford Repair: 1994 e-350 headlight problem, voltage drop test, light combination

Question
The headlights on my van recently went out and the high-beam indicator on the cluster panel was lit.  Every other light on the van work - both interior and exterior.  Was checking the connections and disconnected the right lamp and the driver's lamp came on but only dimly. Plugged the right one back in and both went out.  Next day, got into the van and headlights came on worked correctly.  Later on, they stopped working again.  Have replaced the light combination switch on the dashboard.  Seemed to fix the problem for a few days, and now it is back - more off than on.  Any suggestions?  There appeared to be a little corrosion in the middle connector (ground?) of the driver's headlight plug.  Thanks  -- Greg

Answer
then clean the ground and take a voltmeter and check for good continuity through the ground-you can even check voltage drop through the ground but the instructions is to much for me to type here-google voltage drop test instructions for automobiles. and remember grounds are just as important and voltage supply.