On my 2000 Dodge the left side headlight is not very bright are all. The right side works perfectly. Took build out of headlight and is still dull. Anyone got any ideas.

 

I added wire and soldered all connections and made sure that the grounds measered < 0.003 ohms. This made a big difference in headlight brilance. Or if you have a multi meter measure the voltage on the wires sorry don't know which wires but the DC voltage range . Measure each wire and write down what you get on each side and see if / what the differences are. Could be some corrosion there some where if also. Also is there any wire insulation discolouring.

 

I agree, check the grounds.

 

Your 2000 has a ground circuit default, its always grounded. I had a bulb that done the same thing, replaced bulb.