no dims and screwy gas guage

[lee]

Does anybody know why my dim beams won't work keep in mind I did replace the floor switch checked the bulbs this is in my 68 charger and also I was driving down the road the other day and the fuel guage went empty then 1/2 full then empty then 3rd full can anyone help

[Plumcrazy]

If the problem only occurs with the low beams that would eliminate the headlight switch and the ground for the headlights. A problem with either of those things would also effect the hight beams.  It's also probably safe to eliminate the floor dimmer switch since it was just replaced.

I would unplug the bulkhead connector for the front lighting harness and look there next.

Did you notice if any of the other gauges acted up while the fuel gauge was?
If it was just the fuel gauge it could be the sending unit or the ground for the sending unit.  There's also a 6 way electrical connector down by the parking brake that the fuel sending unit wire goes through. Take a look at it too.