I have a 2000 #7700 XLT with 94K miles on it and like a lot of older trucks, this one is presenting me with a puzzling issue. I saw that I had a high beam headlight out so decided to replace both bulbs, knowing that they were both the same age and if one is out the other would likely follow soon. After getting them replaced, I checked and found that the high beam on the driver's side is still out and the low beam is very dim. The passenger's side is perfect. I even put the old passenger side bulb in there to check if it might be 2 bad bulbs but it does the same thing. Every time I see one of these issues I assume I am not the first one to run accross it so I know someone out there has seen this and knows exactly where I need to start looking. Any help would sure be appreciated. I am by no means electrically inclined but with some direction, can get stuff done. Thanks in advance for any help!

 

Might want to start with checking the ground on the bulb connector on the driver's side.
Use a meter to check from ground to low and ground to high to see what the voltage is and then check ground on the bulb connector to the battery.

The ground lug is on the inner fender, could be loose screw or the wire could be frayed at the connector.