Okay so I figured I would go through the charging system on my truck.. I ohm tested my ground cables and positive cable and found little resistance. The voltage regulator has been replaced with new, a new Motorcraft alternator as well. Both batteries are new within one year and load test good. The issue I'm having is the headlights and interior lights flicker with no load, as soon as I turn the heater on hi the lights do not Flicker anymore.. I know I should be doing a one wire alternator or a 3G set up, but I got a smokin deal on this alternator that was on the shelf. I cleaned all the grounds that attach to the fender well / body area, all the battery terminals are clean as well. I ran a small gauge wire from the alternator bracket to the ground side of the battery and has no effect, lighting still flickers. Is it possible a bad voltage regulator?

 

Any ideas? Well I'll be adding 2 4ga grounds directly to the batteries and installing a 4 gauge charge wire as well just to cover everything..

 

If anybody cares...., after I replaced the charge wire and added 2 new grounds & also cleaned the rest, light flicker is no longer. Also added a good ground from the alternator and regulator

 

I was gonna say sounds like a ground issue, but glad you got it cleared up!

 

Thanks for posting your solution. My truck does the same thing, though I'm waiting for spring to work on the charging system.

 

Yes when I started going through the wiring I also found a lot of corroded ends and some wires only had a few strands.. I'm going to clean the interior grounds tonight, but as far as lighting I have no more flicker.. after I replaced the regulator & alternator I was changing around 15 volts, not so good... when I added new/clean grounds as well as a new 4ga charge wire it dropped back down to 14-14.5 where it should be

 

I need to check mine apparently, they are starting to grow stuff, and i noticed tonight that the lights are flickering randomly... barely enough to notice but still drove me nuts.