Originally Posted by NAPOLEON1949
I have a very very dim low beam on the right side, left side lights up good, is this a ground wire issue or something else? 2004 tiffon allegro on a workhorse chassis.. thx
Yes, it could be a ground. It could be low voltage due to a voltage loss for many reasons. Or, it could be just a bad bulb. So, the very first thing to do would be to check the ground system for that bulb and see if it needs maintenance. Once you determine that, if the ground is a good one, then I'd move on to using a volt-ohm meter and check your voltage at that headlight plug. If the bulb is removable, check it too. If you can do it easily, switch the right and the left one, to see if the problem moves to what was, the good side. If it does, vuuuuallllllla, you've found your issue, a potentially bad bulb.
If the problem does not move to the good side and the dim side is still dim, your bulbs are good and, you've potentially got low voltage to that side. The VOM will tell you what kind of voltage you have. If it's low, you're gonna have to determine why. In many, many cases of manufacturers building motorhomes, they install harness's to the headlights that are too long and you have voltage loss through too much wire.
In other cases, they goofed up and ran the actual wiring/power that's to power up the headlights, through the headlight switch which, in most cases, is not rated to carry the load of the headlights. In those cases, the switch gets hot and has lots of resistance which, causes low voltage to the lights.
Many guys have basically used relays and a new, larger wire to each headlight with the regular wiring, powering the relays. This way, you get BIG power to each headlight. I've seen this done quite a few times and seen the brighter results right off the bat. I did that same *alteration/modification* on one of my Jeeps. I turned on the low beams and they were crap. I then pulled back on one the plugs on the back of the right headlight and, I then placed a 12GA wire directly from the positive post on the battery, to the tang for low beam on that headlight and, it just about doubled the brightness.
Is this your problem? Not a clue. But, you have some answers as to how to proceed in investigating this issue. Please post back with your results so that others may learn.