headlights

My passenger side headlight is dimmer than the driver side. It is so dim I got a ticket for only having one headlight. I already replaced the headlight and it is still dim.
I went to the gas station and hed the mechanic adjust the headlight but that isn't the problem.

I unplugged the driver side head light and when I did it turned off the passenger side as well. So I than went and unplugged the (dim headlight) passenger side and it only turned off that side.

I had my roomate test the wires and they were ok.
I cant afford to take it to the shop So I must figure out what the problem is. If you can help me with any ideas on what could ne the problem, troubleshooting ect would be so appreciated. thank you