I have a 71' Cutlass Vert and my driver side low beam only works when the high beam are on. I re-ran a power wire for a amp and swapped radios. Unplug one radion and plug up the new radion..that simple!! I did have to pull the carpet back by the floor dimmer switch...could that be a lose wire by the switch??

 

Sounds like you have a bad bulb. The outer ones are supposed light in both low and high beam - two different filaments. Since the other one is working, the wiring sounds good.

 

Hey rob, long time!!!! I trying to get ready for Mardi Gras and just want everything working. You said its a bad bulb, even if it works on high beam and not on low?

 

Right. On high beam all 4 bulbs should be on. On low, just the two outer bulbs should be on.
The outers have two filiments, one for highm one for low. It sounds like your low filament is out on that one, a common failure mode on sealed beams. The lows are used more than the highs.

 

Gotcha!!!!!!!

 

I forgot to comeback and say..............Thanks Rob!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

Well, since there was no foul language thrown around, I guess that means you solved the problem!
Always glad to help...