Lights are a good visual indicator when a problem exists. When lights dim at idle and blare up again as rpm increases, you have a weak charging system. Faulty grounds may very well be the cause. Flickering lights isn't the same.
For pre 1970 builds, you have only 1 small wire (typically blue w/white tracer ) from ignition switch going out to the engine bay to power both ignition system and energize the alternator field. ( this wire branched inside the cabin to feed mechanical inst' voltage limiter so a fault there causing flickering is also possible, until this limiter dies anyway).
This worked fine for basic points ignition. If wires, terminals, components, are all good the alternator field would get fully energized.
In 1970 builds, they moved the ignition switch to the steering column. They also increased the size of the contacts inside the switch and the size of those wires. All to get more current everywhere, including out to the engine bay. This would fully supply a solid state ignition module and fully supply a isolated field alternator. As time went on they added other things, like electric choke heater, to this wire/circuit without a issue. At some point they moved that mechical limiter to a different circuit.
So... lets say you find todays problem to be a piss poor add on terminal at the battery. Or the battery ground cable is simply undersize. Or you find the smaller red wire ( supplies everything except the starter ) is the fault. One member knifed the molded rubber boot off that wire to see it had always been a bad assembly. Just never showed before his addons. Bulkhead connections, ALT' gauge connections, etc.., etc... All these faults have been found in any, before and after 1970 models.
This is a good place to insert a truth... There isn't a single point of failure or one single cure all. The madelectrical bypass addresses only 1 point off failure. If I'm going to have a overheat/meltdown, I'd rather it be out there and not under my dash.
OK you found the fault, it's all working again, close the hood and carry on. Could it work better ? Will the ignition switch be the next failure ? Who knows.
To put that pre 1970 blue w/white wire on a relay makes just as much sense as putting relays on the headlight circuits. In fact a new ignition switch would cost much more than a new headlight switch.
All manually operated switches are destine to fail eventually. Old worn switch ( not mentioned above ) might be todays problem too. Overloading a new or good used switch will shorten its life.
Good luck to all
