VCCA Home Forums TECHNICAL - GENERAL Electrical - 6 volt Head lights cause discharging

I have a 52 Chevrolet with a 54 235 engine. The 6V charging system works properly in all situations except when I turn on the headlights, even at high rpms the headlights are dull and the amp gauge shows a discharge condition.
- The vehicle has a new wiring harness (original style)
- I have tried both a 10&1/2 Inch and a 9&1/2 inch length generator with the same result
- I have tried the original voltage regulator and a new after market regulator with the same result
- The park lights are bright and operate showing a charge condition
- I bypassed the dimmer switch with no change
- I cleaned the area of the headlight grounds
I’M STUMPED?
Everything is fine if I don’t get caught in the dark……..not a good plan.
I welcome any and all suggestions.

Dave

question which bulbs are you using ??
wondering if the bulbs or one of the bulbs is faulty and pulling and extra load. remove the bulbs from the sockets and see if there is a discharge on the system when turned on. if so then you know it is in the wiring, if not then the bulbs.
start simple and work back.

The 52’s have seal beam headlights so not a traditional bulb but I think it’s worth trying other head lamps and see what happens.
Thanks for your input.
Dave B

disconnect the sealed beams and see what it does, do one at a time, see if either has an impact on charge/discharge. then disconnect both. turn on turn off. see what happens.

could also be a short or ground in the light switch ??

I was thinking about the light switch and have found a spare in my parts collection. Being a senior, the thought of crawling under the dash is daunting to say the least.
I will try your headlights suggestion today.
Thanks for your help.
Dave B

Wonder if you need to adjust your regulator to up the output a little so you're still charging with headlights on.

Removed headlights and tried each individually, cleaned up the electrical contacts and applied dielectric grease.
No change.
I have dismantled an old headlight switch and cleaned up the components and applied dielectric grease to contacts, I will install it in the next couple days.
To ScottCrawford, how does one up the output on the regulator?
Please and Thanks
Dave B

A suggestion, Dave. If you don't relish the thought of crawling under the dash to get at the light switch, you can also get at it by taking off the panel that the voltage regulator is mounted to, then worming your way through all the wires to reach it.

Yes, this will take some figuring out.

Have you had the generators tested for output? I also wonder if you have an earlier model generator that does not have enough capacity.

What are the voltage readings at the battery under different conditions?

Is the voltage regulator frame properly grounded to the car body? If the firewall has been painted the mounting screws might not have good contact with the body. The regulator works fine under light loads. At higher loads the increased resistance to ground could create a problem.

Dave,
I would follow Rusty's train of thinking. What happened with mine was....even at high idle, the regulator just wasn't allowing the generator to feed enough voltage to the battery to keep it charged. I saw the same discharge symptom with headlights. The fix depends on your regulator. The 201 regulator has a tab you bend to adjust...the 301 regulator has screws you adjust with. I had a 201 and bent the tab til I got about 7 volts towards the battery. That has my ammeter looking a little better in all cases.

Thanks to everyone for the good information. I will attach a ground wire to the VR frame as my car was a total repaint so I’ll start with that, as well I will do a repolarzation.
My generator is a professionally remanufactured unit:
- it started out as a 9 & 1/2 1953 unit #1100018
- the armature is from a 1951 unit #925348 from a #1879022 generator
- the generator end is from a #1866052
Yes it is a cobbled together misfit.
An original #1100018 (according to my service manual) has the generator field and positive posts reversed, I have assumed that because the armature and end is from an earlier unit the polarity would be the standard hookup. What do you think?
It’s a rain day (more like a rain week) on the Island so the garage is a good place to be.
Dave B

Does it have band you can take off to see the brushes? Field post will go to the coils in the case. The other 'GEN" or "ARM" post goes to one brush and the other brush is grounded.

I agree its a good idea to fix the grounds and polarize first. Don't be in a hurry to turn up the voltage until you understand for sure what is happening.

From your description, it sounds like the generator (or regulator) cannot provide enough current. If the voltage is fine with the lights off (7.5ish with a fully charged battery and the engine running above idle), but it cant keep up with the lights on, that is a current issue not voltage.

There are 3 relays inside the regulator. When setting up a regulator from scratch, there are air gaps and points gaps to set in addition to the springs, but on a recently working system the only thing that normally gets adjusted is the voltage, as described in Scott Crawford's post. However, if the voltage is already regulating normally with the lights off, turning it up is just going to make it boil the battery with the lights off.

Back to those 3 relays....

One is a cutout. It connects the generator when the engine is spinning. It is probably set at something between 4 and 6.3 volts. The shop manual will know for sure. It's purpose is to disconnect the generator when the engine is not running, and prevent it from trying to run like a motor, and discharge the battery, or burn up while the engine is not running. If it is open with the engine off, and pulls in when you start the engine and rev it up, it is working normally.

The second is a current regulator. This, surprisingly, sets the "size" of the system. Generaors do not self-regulate current like alternators, so the setting of this relay determines what maximum output will be. If it is set at 40 amps, and you install a 20 amp generator, that 20 amp generator will happily burn itself up trying to make 40 amps. The current regulator really should be thought of as a safety device, because in normal operation it wont do anything. Why? Because there is a voltage regulator too, and on any normal day the battery and accessories won't pull anything close to 40 amps. On some day when the battery is almost dead though, and its cold, and the heater is on, and headlights, and the radio, wipers if electric, etc., the voltage will be low and the generator would happily put out current way over it's rating if asked. The smoke might come out.

The current regulator should have been previously set to 40 amps (if the car has a 40 amp generator, 30 if a 30 amp generator etc.), and it will regulate there until the battery gets full enough and or accessories get turned off enough that 40 amps isn't needed anymore. Then the voltage will rise to the normal system voltage, and the voltage regulator will take over.

I'm thinking you really need to have that generator tested to see if it can put out it's rated current. It should want to do MORE than rated current if allowed. If it can't, then turning up the current at the regulator won't help, that's only a safety device.

The third relay is the voltage regulator, and should be set at about 7.5 volts. It is temperature dependent, and the manual will have a table of voltage vs temperature, or a graph or something to you can see what the voltage should be at the temperature the regulator is at while you are setting it. If the battery is notoriously under or overcharged over a long period of time, you might turn this one up or down about two tenths of a volt, but most cars will like the factory setting.

The voltage regulator voltage will be about the same (7.5-ish) at any time the generator is keeping up with demand, with the engine above idle and a fully charged battery, lights on or off.

It sounds to me from your description like the generator cannot produce enough current to keep up. it could be the current regulator setting, but most likely not. It is a setting nobody ever changes because there is no need as long as the generator is one of the same current rating. The setting makes no difference in normal operation.

PS I saw that you tried 2 different generators. If polarizing and grounds don't fix it, I would get them both tested.

Thanks bloo for your excellent response, very helpful in understanding these old systems. It’s hard to know the output of this generator given the rebuild components as it is likely different from the manual specs for its unit number. I accept your advice that having it tested is a good idea.

I did install a different light switch but nothing changed.

Thanks again to all the helpers!
Dave B

Hi bloo
I removed the band and the set up is as you described, Field post goes to the coils in the case, one brush is grounded, the other brush goes to A post. Is this the “normal” set up?
Dave B

thing that puzzles me is that you state the headlamps are dim
...are they dim when you turn them on ?
seems that with a fully charged battery that they would be bright and vivid then as they drained power they would slowly dim as they drain the battery/ power source. i know on my 1929 that with out the car on i can turn on the lights and they are bright and vivid for a good while, takes a while to drain down the battery to make them dim.

1-can you meter the output from generator to the battery ?
...meter positive to wire output from generator/regulator (hot) and meter ground to chassis/frame.
...a 6v system should be charging around 7.2v this is what you should be getting out of regulator

2-try and jump the ground
...run a ground wire directly from the battery to the ground terminal on the headlight terminal connection
...this will let you know if you have a ground problem. if lights are bright and vivid you have a ground issue somewhere, if not then not ground

if not a ground issue
3-meter the power at the headlight terminals
...see what you have for low beam & high beam when on and when off
...use the ground terminal in the headlight terminal

Hi Dave

Simple answer... yes your internal generator wiring is normal and correct.

And now a silly question...
Have you checked to make sure your sealed beam lights are 6 volt and not 12?

That might explain the dim lights, but still wouldn't explain the discharge when they are on.

What happens in the 1929 is going to be different, at least if it is original because the charging system is very small in current capacity and there is no voltage regulator. For one thing, the changes are going to be much slower.

In any typical car with an Alternator, or a larger 2-brush Generator with a 3-unit regulator like what is described here, the behavior will be more or less as follows:

When the system is "keeping up", for instance if it is capable of 40 amps and the car is drawing something less that that, the voltage regulator will oscillate on-off and hold the voltage to whatever the voltage regulator is set to. That is often around 7.5 volts.

The natural voltage of a fully charged 6v lead-acid battery is 6.3 volts. It can be a little higher due to "surface charge", maybe 6.6v or more, that will go away very quickly when you put any load at all on the battery, You can consider the battery voltage to be 6.3v when it is full.

When the system is keeping up, the source of current is the charging system. The accessories can draw some current, and the battery can draw all it wants to become recharged (possibly after cranking the car). The system voltage is chosen so that the battery taper's its own charge, and winds up just full or a wee bit over. As previously mentioned, the voltage that accomplishes that is about 7.5 (temperature dependent), and so that is what the voltage regulator is set to.

The headlights are effectively running on 7.5 volts. It is a slightly less because there is loss in the wiring and switches, but I am going to ignore that for this discussion because you have that loss in the switches and wiring no matter what the system voltage is.

The instant you exceed the charging system capacity, and the generator cannot keep up anymore, things change quickly. It could be because the system is broken (bad brushes or something), and cant supply the current. It could be because you have installed a bunch of accessories that exceed capacity of the system and turned them all on.

For whatever reason, the system does not keep up. The generator continues to charge at it's maximum current. The generator can no longer push the system up to the 7.5 volts that the voltage regulator is set to, because it has nothing left over. Current begins to be drawn from the battery to make up the difference in necessary current.

Battery voltage is 6.3, so the voltage drops from a regulated 7.5v to the battery voltage of 6.3v. If there is surface charge there can be a slight delay, but in practice it is almost instantaneous.

That is all a bit of an oversimplification, but bear with me.

You can see a 0.2v change in headlights. Maybe even 0.1v on a 6 volt car. Half voltage is not half brightness in a light bulb. They drop off fast when voltage falls. You just lost 1.2v when the generator's capacity was exceeded. 1.2v is HUGE.

Now your lights are dim. What happens next?

Well, the poor generator is doing all it can. If the generator is healthy it will try to exceed its rating to bring the voltage back up, but the current regulator will hold it back and it cannot. If the generator is defective and not able to produce rated current, the current regulator wont do anything because the current is still under the generator's rating.

Since some current is being drawn from the battery now, it will continue to discharge, and the lights will continue to get slowly dimmer as the battery voltage falls as the battery discharges. Eventually the ignition will get weak due to the low voltage and stop working. How fast this happens depends on how much current is being drawn. The current I am referring to here is the difference between what the generator can do, and the current being drawn.

Here's a completely made up example, just to illustrate what happens:

We have a broken generator on a 40 amp system making 10 amps. We are drawing 15 amps total with some lights on. Since the generator makes 10 amps, 5 amps is what is being drawn from the battery. On a 50 amp-hour battery that should go 10 hours before it is fully discharged. You probably won't get anything close to 10 hours in practice because the voltage is falling the whole time. At some point the already dim lights will be completely unusable, and or the ignition will stop working.

Now, we turn the lights off. The ignition draws about 2 amps. That leaves 8 amps to charge the battery. The voltage slowly rises. As the battery starts to get full, and it is going to take a LONG time with this broken generator, a point will be reached when the battery does not need all 8 amps anymore to continue topping off its charge. Then the voltage will come up to 7.5V again and the voltage regulator will start regulating.

This process works the same if the system is healthy but you just have too many accessories installed and turned on. It also holds true for alternators. As long as there is current capacity (amps) left over, the car runs at system voltage (about 7.5v on a 6 volt car). If you exceed the system capacity the voltage will be 6.3v and falling.

I must admit this has a level of complexity that is proving difficult for a retired accountant, but it is very interesting and challenging.
- I did check my headlights and they are six volt.
- My battery is a New Delco 6v bought 2021.
- The headlights are bright when turned on without the engine running.
The charging system functions properly during daylight travel, heater on, radio on, signal and brake lights employed. The voltage meter acts normal, a charge push after starting and settles in just above neutral, reflects signal lights flashing etc. The running lights are managed by the charging system but headlights (high and low) show a discharge approximately halfway between the middle and full discharge markings on the amp gauge (slightly more discharge on high beam).

So if I only drive during the day I am fine. I think bloo is correct in believing my generator output may be lacking and I will have it tested.

The new 6v regulator I have is made by Standard Motors and is meant for a 45 amp system, I believe my existing generator (if it was working properly) is good for 35 amp so the two are not a good match.

It’s been a fun adventure and I am learning a lot but I also forget a lot. This car was my daily driver starting in 1967 and used all year even during our very cold winters, the system worked fine back in the day, go figure!
Many thanks
Dave B