Hey guys,

I'm the worst at figuring out electrical issues over anything else. But in the case of the 55' I do have a basic understanding of how the generator and regulator work. Still though I'm at kind of a loss, I also don't really know how to use a multi-meter that much so testing is kind if beyond my knowledge. But maybe describing the situation will make it obvious to someone who knows more about power systems then I do.

When driving down the road with the headlights on, that is headlights and the internal dash illumination, the yellow GEN discharge light will come on after a short period. At first and for most of the time it's so dim that it's annoyingly hard to tell weather or not it's really on or just catching some of the glow from the surrounding back-lighting. The only way to be sure is to turn off the lights for a moment. Sometimes it isn't really on and sometimes it is so the issue must come and go I suppose. But after prolonged driving the light will get brighter and more obvious.

Here's where it seems to be opposite then what you'd expect. Rather then coming on at idle then fading out when you increase RPMs, for me it's opposite. Running the engine at speed will bring the light on and it'll go out when stopped or at least dim considerably. I was hoping that this was just a quirk of old mechanics that maybe it was normal for the GEN light to be on very dimly while the headlights are on.. being a 6 volt car and all.

But the other night, by the time we got home the light had gotten pretty bright and I noticed while pulling into the driveway that the headlights and interior lights had dimmed to an almost minuscule level. It was such a slow and subtle dimming I hadn't noticed till we pulled into the house.

So obviously the battery IS gradually discharging without a chance to charge is seems.

This issue only happens when the headlights are switched on though, while driving in the day things are fine. What I'm lead to believe is that the generator is only supplying JUST enough to run the car with no accessories, that or the regulator is preventing it.

The Generator has been rebuilt and bench tested, and the Regulator is brand new and a modern model bought from an auto-parts store. I've also polarized the generator since last time the battery was connected to the car. Though I have had a battery tender hooked up to the car since then due to the battery going dead from prolonged (one or two week) sitting in the past.

I don't have an answer for you and wish I did as I have had a similar problem for the past 5-6 years, it just started one day after working normally for all the years previous  and that I haven't been able to resolve. Mine is a 12V system on my 1960 truck but the problem is the same. I'm usually pretty good at electrical but this has had me stumped, it has never caused a problem, it's just annoying seeing the GEN light lit dimly at higher rpms. It drove me crazy on a recent trip going from Calif across Arizona headed to New Mexico, drove six hours straight at night with the air conditioning on but it never caused a problem, ended up doing 2100 miles on that trip in 100+ temps. I knew it was charging, at idle the lights were a little dimmer and you could hear the air conditioning fan slow down, thats pretty normal and as soon as the rpm increased lights got brighter and fan sped up. Over the past few years I have changed generators, regulators, battery, redone all the grounds, done all the electrical test and I haven't found the problem yet. I've never had a battery issue, it can sit for a month or two at times and cranks right over.. Hopefully someone will have some insight as to what causes this.

55 6v positive ground...First switch to a neg ground.  I would suggest also switching to a 12v system. that being said
    using a multi meter is easy, buy one from Harbor Freight, $4  set it on DC... make sure it turns on and you can see the numerals.
 If you can have someone help you, start the car, place the Red lead on the cars engine   and the Black lead on the Gen field.
Remember the car is positive ground.
  You should get a voltage of about  6 to 8v  at idle, now speed up the RPM and check the reading, you should be up at 8v steady.
Now take the Red lead and place it on a clean place on the block, and the Black lead on the Voltage Regulator  (VR)
and take a reading at idle then at a higher RPM. Finally check the battery, check voltage at both idle and higher RPM. This will
give you the base for your car.
  VR of the period are mechanical, and they have adjustment to them... taking off the cover you will see the adjustments but you need
a service manual or some more knowledge then I have to adjust them.
  At the beginning I recommended that you switch to a Neg ground system.. It was found that a positive system drains the battery fast
and also corrodes more then a Neg ground.
http://www.gomog.com/allmorgan/polarity.html
If you drive the car a lot, I would really suggest a switch to 12v Neg..
http://www.how-to-build-hotrods.com/6v-to-12v.html

But I do understand the wish to keep a car "original" 
You can also help your electrical by using a solenoid on the headlights. This takes the amps out of the headlight switch
and puts them right at the headlights, remember unless you've done a new wiring harness that wire and switch is 60 yo
http://www.allpar.com/fix/electrical/headlights/index.php
All the best

[quote][b]Sanddoc (10/24/2016) It was found that a positive system drains the battery fast
and also corrodes more then a Neg ground.

Sanddoc, I would be interested in your source for that claim, as my experience has been just the opposite. I had also heard that those were the reasons for Henry's obsession for retaining positive ground, and thus FoMoCo's delay in adopting neg. grd. in the face of otherwise universal industry (GM, etc.) adoption. My ignition points last (seemingly) forever, and all my body ground connections stay clean. The battery issue is not so clear though, since the mysteries of regulator service/adjustment can so easily be ignored by plugging into a smart charger occasionally while the car is garaged. My current battery is 9 years old and always starts the car without issue.

6 VOLTS/POS. GRD. NW INDIANA

Years ago had the same problem with my 56 Victoria, I put new brushes in the generator problem went away.  

I think Lou has the answer. 
A generator may test just fine at an auto parts store, but in actuality, may not be doing the job.
I'd do the brushes first thing. Cheap & easy

57 Jim: I can't diagnose your apparent problems, however from your post, the issue of heavy load causing dimming at idle, is normal with generators. It's one of reasons that they were replaced by alternators some years ago, especially with the myriad of accessories on modern vehicles, a generator just won't supply enough voltage at idle to keep up.     


Paul

Thank you, I think I stated in my post that the dimming at idle is normal, I understand that. What I forgot to add was that the generator idiot light comes on dimly at higher rpm's even in the day time with no load? It's like there is 1-2 volts going through it. I've changed generators, changed brushes, changed brush springs, even changed to an earlier style end plate that has the different type brush holder and springs..

What a mysterious issue!

I've had that generator in the shop twice. It wasn't working at all the first time, had it rebuilt and it still wasn't working, brought it back and then it worked after that.. at least...

Put in a different battery and see if the problem goes away, your battery may be on the way out, also check the regulator.