1929 Model A - Headlamp issues

[Ace1347]

Good afternoon, I am now the proud new owner of a 1929 Model A Roadster.
I am reaching out for input in respect to the headlamps. The car has been converted to 12 volts and when I brought the car home the headlamps were fine. I noticed they go dark at a stop and once the idle picks up they grow bright. I plan to take a look Saturday morning but am looking for input if possible. A longtime lurker to this site and excited to interact more often.

Thank you in advance!

[Herb Concord Ca]

Welcome, if your new A has a generator, what you observed is common. Not much you can do about it, other than changing to an alternator.

[Gene F]

"snug" the belt. The battery being up helps too. When you pull up to a light and stop you really want your amp guage to be just barely on the positive side. If not come back, and we can tell you how to adjust the brush.

[Ace1347]

Thank you! I appreciate the input. I am not very car savvy. Please excuse the odd question. I remember as a teen my old VW having a generator and the headlamps were fine. If you don't mind my asking - Why would that be the case?
I thank you in advance for any input.

[Joe K]

Originally Posted by Herb Concord Ca

Welcome, if your new A has a generator, what you observed is common. Not much you can do about it, other than changing to an alternator.

I think I would disagree. Maybe a change in brightness, but that would be a battery issue. Going completely black means that the lights are being lighted by something other than the battery, perhaps the generator under the influence of a defective voltage regulator?

I'll reference to the best Model A Circuit diagram in the world (there are others.) Any investigation you do will be referencing this diagram. It is the place you start in diagnosis.

https://lesmodela.files.wordpress.co...ng-diagram.pdf

Now looking at this one keeps in mind a 12V conversion doesn't change much except the voltage. UNLESS those who converted it did something seriously different than this diagram - which is always possible.

Referencing the diagram, keep in mind the "yellow" wire is the one which "feeds" your lights and your horn from the generator cut-out. Also see that a further yellow/black wire passes from cut-out to the junction box connection/pole. This is your generator connection to the car/battery.

See also that the ammeter connects together the two "poles" of the junction box. For all practical purposes an ammeter is a "closed circuit" meaning no resistance. The two poles are connected together electrically with the bonus feature you can read how much current passes between poles.

See also the additional yellow wire passing from the "other" junction pole and connecting to the black wire from the battery. Thus Ammeter is a way to see how much current flows to the battery, or from the battery to your car.

Somewhere along this path is likely your issue with "connection." You may be running only on generator voltage which is describing the symptoms you see. You don't say if your generator is "regulated" which I might expect as an open circuit Model A generator will generate as much as 32 volts which will burn out your light bulbs. (It is possible that your generator is an uprated Model A generator. This is possible with the correct voltage regulator. Although many retro-fit with a modern genny simply on the basis of reliability - which for most is the point of a 12V conversion anyway.)

Check each connection in turn. Use (my favorite) No-Al-Ox which is a conductive grease that electricians used to use on aluminum wire back when the code allowed you to use it. The grease contains graphite which itself is conductive and will keep and maintain any electrical connection. Thus you can "be sure" each connection is made as best as it can be made, and the grease seals it and keeps it this way.

Good luck. Diagnosis/solutions to problems that crop up is part of the attraction to many of the hobby - and what sets the Model A apart is that it is possible to do this yourself.

Joe K

[Gary WA]

Sponsored Links (Register now to hide all advertisements)

Battery! have load test at auto store and must have a good ground!Clean and bright.

[TerryH]

Do your lights just grow dimmer at a stop, then brighter when you start driving? Also, is it possible your car has an alternator when it was converted to 12v? At a low idle the alternator will not put out much, but charges plenty as soon as the engine speed picks up when starting out.

[Ace1347]

I appreciate the input and will report back once I have taken a closer look. The intent was to spend some time with it tomorrow but My wife just reminded me there are more important things to do on Christmas Eve. I will report back very soon.��

[rotorwrench]

The VW beetles were manufactured and exported to the USA in a time frame where all generators were two brush types with voltage regulators plus the headlamps were of a moderate wattage rating. Your model A may have halogen bulbs which are higher wattage then combine that with having the tail light and possibly the brake lights, it could have a fair amount of current being drawn at a stop.

Original model A electrical systems were rudimentary at best. The 3-brush generator at high amp setting could just barely keep up with the lights on. They had no voltage regulator since the battery regulated the voltage. The 3rd brush adjustment set the current output. All they had was a cut out relay to bring the generator on line after start up.

If your car has been setting unused for a time then the battery may need attention and condition of terminal connection may be less than optimal. Even if it has an alternator with internal regulator, a weak battery and high draw headlights could give the condition stated.

[ModelA29]

Originally Posted by Ace1347

.....My wife just reminded me there are more important things to do on Christmas Eve.

Yes - it's time to start Xmas shopping.

[Chuck Dempsey]

Welcome to the 'Barn.... Enjoy

[Dick Carne]

I initially experienced the same thing with our cars years ago, so I first converted to a six volt alternator. That helped, but I still noticed some dimming whenever the car would be stopped. I then converted to 12 volts (and 12-volt alternator), and that seemed to resolve that issue, however, I've also noticed some other things may need to be changed out as a result. For instance, the starter on our Town Sedan would slam into the flywheel gear, and several of the horns no longer have the nice old "ahooga" sound, but rather more of a loud "splat" (I've since had to replace the Sedan flywheel gear). Despite the other cars not having issues with a six volt starter, the conversion of field coils in the Sedan starter seemed to resolve that issue for that car. I plan to have our touring car horn rewound for 12 volts after the first of the year.

But with all of that said, there are now several variations of LED bulbs that are now available that do not have near the same draw that a traditional bulb does (these were not available when I converted our cars to 12-volt systems). So my first recommendation would be to possibly consider changing to LED bulbs to see if this might resolve your problem - regardless, I would certainly recommend LED's on all stop and tail light applications, whether six or twelve volt. Others may care to weigh in on this thought as well. Good luck to you on this, and welcome to the "group"!

[Gene F]

I put an amp probe on my LED headlamps, and they hardly draw anything.

[Synchro909]

Even if the battery is decent, what you describe is common. Once the engine revs drop to a certain level, the alternator stops charging, then starts again when the revs rise. I am assuming the car is fitted with an alternator if it has been converted to 12 volts. Alternators need more revs to start charging than a generator - that's why they have a smaller pulley.
The first thing I'd do has already been suggested - test the battery. You don't need to take it anywhere to get a good idea of its condition. With engine off, check the battery voltage with nothing turned on. If it is 12.6 volts, it is charged so turn on the headlights and try the horn. If you hear nothing or even a groan, the battery is in need of replacement even though it shows full voltage.
Here is a guide to interpreting your voltage reading. https://www.google.com/url?sa=i&url=...AAAAAdAAAAABAE

[Ace1347]

Update!
I appreciate the responses and I am happy to report it was a loose ground. I am happy to have resolved the issue. Work and rain has kept me from driving the car recently. I plan to take her out for a cruise this weekend.

[David in San Antonio]

@Ace1347 - Welcome to the hobby. I’m also a newbie. As suggested above I switched out the headlight and taillight bulbs to LEDs. It’s SO much better! The headlights are really useful now. And the LED taillights/ brake lights are much more visible to the drivers behind. This was particularly reassuring. And as a bonus the current draw is minimal. When I hit the brake pedal or turn on the headlights the ammeter barely moves!

[Ace1347]

Originally Posted by David in San Antonio

@Ace1347 - Welcome to the hobby. I’m also a newbie. As suggested above I switched out the headlight and taillight bulbs to LEDs. It’s SO much better! The headlights are really useful now. And the LED taillights/ brake lights are much more visible to the drivers behind. This was particularly reassuring. And as a bonus the current draw is minimal. When I hit the brake pedal or turn on the headlights the ammeter barely moves!

Thank you!! That is definitely a project I will contemplate very soon.

[Kurt in NJ]

the first thing i noticed when i put in halogen bulbs is the there was almost no change when the generator went off charging at idle, before when i had 50 cp regular bulbs it was almost like they were turned off.