Hi I'm new to this site and my car. Need to get it inspected but having a problem with the headlights. On low beam all lights are dim, on High they are OK. At least they are bright. Need some ideas were to start looking for the problem.
Battery charge level is the most important. Everything in your car is run off the battery. The alternator puts out only enough power to recharge it not run the actual devices that draw current.
As such you need clean contacts and good grounds. The one switch that your lights go through beside the light switch is the dimmer switch on the floor. Years of slush covered boots have probably corroded the contacts inside so that the switch isn't making a good connection on one side of the contacts.
A newer one wire alternator will help also as it is designed to run all of the electrical devices in a modern car. Down side is it outputs twice to four times the power of the old alternator so it requires a bigger wire to carry the added load. The wires in your car were inadequate when it was new. Add three times the rated power level from a bigger alternator and they become a fire hazard.