Ammeter - charge/discharge

[A TRUCK]

Just a quick question - While my '29 Model A Pick Up is idling, the ammeter sits around "0" and whilst driving it starts to move towards "charge" 20. However, when I switch my lights on it goes straight to "discharge" 20 and just sits there without moving towards charge or moving at all.
Anybody experience this before? - Your help is much appreciated....

[Jim/GA]

Do you have stock headlights or have you installed higher power bulbs or halogen bulbs?

Do you have the stock generator?

Are you still 6 volts?

[A TRUCK]

Originally Posted by Jim/TX

Do you have stock headlights or have you installed higher power bulbs or halogen bulbs?

Do you have the stock generator?

Are you still 6 volts?

I have the stock headlights and have installed 32-50 candle power bulbs. Yes, generator is stock and I am still on 6 volts.

Thanks Jim

[Joe K]

Repop meter or one of the old, good ones?

Meters new or old are notorious for being inaccurate. More so new.

Your general direction on charge/discharge seem correct (it can be "0" if your generator charging is quite low and ignition use balances your generator output.) But that dramatic drop to more than 20 amp discharge seems a bit over the top.

Do you have both high/low beams? Both filaments "on" at the same time might cause extreme current draw. Check that your wiring is not crossed between the low and high circuits. A cross/connect can cause BOTH filaments to be on with no discernible difference between high and low.

Just throwing out ideas here of things to check.

Joe K

[Tom Endy]

Originally Posted by A TRUCK

Just a quick question - While my '29 Model A Pick Up is idling, the ammeter sits around "0" and whilst driving it starts to move towards "charge" 20. However, when I switch my lights on it goes straight to "discharge" 20 and just sits there without moving towards charge or moving at all.
Anybody experience this before? - Your help is much appreciated....

The Model A stock generator does not incorporate a voltage regulator. Voltage regulators came out a few years later and were a mechanical relay box bolted to the fire wall that monitored the battery status and the electrical load and adjusted accordingly and kept the battery fully charged.

A Model A generator has a fixed amperage output. It is generally adjusted to a nominal 8 amps output. When driving during the day the ammeter shows plus, which means the generator is charging the battery. When driving at night the headlight load is more than the 8 amps the generator is putting out. The battery has to make up the difference. The ammeter will then show a discharge. The amount is depending on what size bulbs you have installed.

The modern alternator has a built in solid state voltage regulator that constantly looks at the status of the battery and the electrical load requirement and adjusts the amperage output accordingly and keeps the battery fully charged.

When alternators came out they were all 12 volts. Since then suppliers now sell alternators converted to 6-volt positive ground for the Model A. This is really the way to go if your Model A is a daily driver, though many purists frown on them.

The alternator regulator circuit will monitor the battery and the electrical load and keep it fully charged regardless of the driving habits of the owner.

In the old days it was common to see old cars on long stretches of highway with their headlights on during the day. This was done to drain off the excessive current the generator was putting out so it would not over charge the battery and boil the water out. people who drove their Model A's a lot at night always had a low battery that did not last them long unless they had a means to re-charge it during the day.

Tom Endy

[QGolden]

Sponsored Links (Register now to hide all advertisements)

That is a nice write up Tom. Along the same lines, could one add a Bosch or some such (external) voltage regulator to the charging system? I know that Tom sells an internal unit. But if you were not concerned with originality could an external one be used?

[A TRUCK]

Originally Posted by Tom Endy

The Model A stock generator does not incorporate a voltage regulator. Voltage regulators came out a few years later and were a mechanical relay box bolted to the fire wall that monitored the battery status and the electrical load and adjusted accordingly and kept the battery fully charged.

A Model A generator has a fixed amperage output. It is generally adjusted to a nominal 8 amps output. When driving during the day the ammeter shows plus, which means the generator is charging the battery. When driving at night the headlight load is more than the 8 amps the generator is putting out. The battery has to make up the difference. The ammeter will then show a discharge. The amount is depending on what size bulbs you have installed.

The modern alternator has a built in solid state voltage regulator that constantly looks at the status of the battery and the electrical load requirement and adjusts the amperage output accordingly and keeps the battery fully charged.

When alternators came out they were all 12 volts. Since then suppliers now sell alternators converted to 6-volt positive ground for the Model A. This is really the way to go if your Model A is a daily driver, though many purists frown on them.

The alternator regulator circuit will monitor the battery and the electrical load and keep it fully charged regardless of the driving habits of the owner.

In the old days it was common to see old cars on long stretches of highway with their headlights on during the day. This was done to drain off the excessive current the generator was putting out so it would not over charge the battery and boil the water out. people who drove their Model A's a lot at night always had a low battery that did not last them long unless they had a means to re-charge it during the day.

Tom Endy

Tom, thank you for your very detailed information - you have been a great help! I am not too fussed about switching to a 6 volt alternator, I just want it to be more reliable.


Basil

[Tom Endy]

One of the best kept secrets in the Model A hobby is Becker's Antique Auto Electric in Ohio. Larry Becker has been selling complete Model A 6-volt positive ground alternators for years at a bargain price. They come with a complete mounting kit and an extended warranty. Another plus is that his alternators are putting out current as soon as the engine is running at idle. You don't have to rev the engine to 1000 rpm for it to kick in like most others.

Tom Endy

[Mike V. Florida]

I get confused when I read stuff like this. The "problem" you state seems to be the amp meter or both filament's are coming on at the same time. How is an alternator going to help this? When someone states, " I just want it to be more reliable". More reliable then what? I have about 20,000 miles on mine, day night, rain, shine and the genny has never given me problems. The model A generator works just fine on the Model A. I even believe Model A's were used as everyday drivers with the stock generator in it's day.

Now, if you are going to add non stock items that draw more current then the original design, like halogen bulbs that give more un focused light in dull reflectors thus making one think it is safer to drive at night but really just blinding on coming cars, then an regulator or alternator is your best bet with a 30-0-30 ammeter. I've said it before if you properly fix what is not right on your vehicle then all you need is stock. If it makes an owner feels better to have these things on there car, then fine go and get them, but you do not NEED them.

Want to have and need to have are two different things that often get confused on this forum.

[Patrick L.]

20 amp charge from original generator is too high, 12-14 is about as high as you want to go. The 20 amp discharge has me thinking that maybe your headlight wiring is grounding/shorting itself at the connectors. To check to see if the ammeter is reading somewhat correctly, just step on the brake pedal and see what the stop light[s] are/is drawing. Depending on the CP of those bulbs it should be in the 6-8 amp range.

[A TRUCK]

Originally Posted by Mike V. Florida

I get confused when I read stuff like this. The "problem" you state seems to be the amp meter or both filament's are coming on at the same time. How is an alternator going to help this? When someone states, " I just want it to be more reliable". More reliable then what? I have about 20,000 miles on mine, day night, rain, shine and the genny has never given me problems. The model A generator works just fine on the Model A. I even believe Model A's were used as everyday drivers with the stock generator in it's day.

Now, if you are going to add non stock items that draw more current then the original design, like halogen bulbs that give more un focused light in dull reflectors thus making one think it is safer to drive at night but really just blinding on coming cars, then an regulator or alternator is your best bet with a 30-0-30 ammeter. I've said it before if you properly fix what is not right on your vehicle then all you need is stock. If it makes an owner feels better to have these things on there car, then fine go and get them, but you do not NEED them.

Want to have and need to have are two different things that often get confused on this forum.

__________________________________________________ _____________


Thanks for the REAL encouragement Mike V. Florida!!! I'm new to this forum and am just searching for answers, not people like you putting others down!

[A TRUCK]

Originally Posted by Patrick L.

20 amp charge from original generator is too high, 12-14 is about as high as you want to go. The 20 amp discharge has me thinking that maybe your headlight wiring is grounding/shorting itself at the connectors. To check to see if the ammeter is reading somewhat correctly, just step on the brake pedal and see what the stop light[s] are/is drawing. Depending on the CP of those bulbs it should be in the 6-8 amp range.

__________________________________________________ _____________


Thanks for your feedback Patrick L

[whirnot]

Originally Posted by Patrick L.

20 amp charge from original generator is too high, 12-14 is about as high as you want to go. The 20 amp discharge has me thinking that maybe your headlight wiring is grounding/shorting itself at the connectors. To check to see if the ammeter is reading somewhat correctly, just step on the brake pedal and see what the stop light[s] are/is drawing. Depending on the CP of those bulbs it should be in the 6-8 amp range.

Mine charges 20 amps at higher speeds and I have no problem. I was initially concerned about this until I read that Tom Andrews recommends the generator be set at 10 amps charge at idle. I do admit for long drives I turn on the headlights if I remember.

[Purdy Swoft]

Originally Posted by QGolden

That is a nice write up Tom. Along the same lines, could one add a Bosch or some such (external) voltage regulator to the charging system? I know that Tom sells an internal unit. But if you were not concerned with originality could an external one be used?

Actually there are three voltage regulators available for the model A type generator. I use the Fun Projects can style voltage regulator. The Fun Projects regulator fits in place of the cutout and no modifications to the generator is necessary. The regulator looks like the early style cut out but functions like a modern voltage regulator. Fun Projects has a web site. I have used the Fun Projects regulators for years with good service. Try fun projects . com

[Mike V. Florida]

Originally Posted by A TRUCK

__________________________________________________ _____________


Thanks for the REAL encouragement Mike V. Florida!!! I'm new to this forum and am just searching for answers, not people like you putting others down!

What are you talking about? I think you need to re-read what I wrote.

I did not put you or anyone else down, if you want to spend money thinking an alternator is more reliable then a generator, go ahead buy it. I don't think an alternator will change your symptons. I think it is that both headlamp filiments are on at the same time or you have a bad ammeter.

If trying to save someone money is putting them down well, we have a different idea of what a put down is.

[marc hildebrant]

Purdy,

With regard to the fun projects part; while it does regulate the voltage, it doesn't perform the regulation in the same manner as the old three/two unit voltage regulators. The fun product device uses a "shunt" type of voltage regulation while the older voltage regulators devices regulated by reducing the field current to maintain the output voltage constant.

The fun projects circuit works, but in a different manner.

Marc

[marc hildebrant]

A Truck,

Mike V has given you some good information to think about. I suggest that you read the reply and take it as someone with experience trying to HELP you.

Marc

[Mike V. Florida]

Originally Posted by Purdy Swoft

Actually there are three voltage regulators available for the model A type generator. I use the Fun Projects can style voltage regulator. The Fun Projects regulator fits in place of the cutout and no modifications to the generator is necessary. The regulator looks like the early style cut out but functions like a modern voltage regulator. Fun Projects has a web site. I have used the Fun Projects regulators for years with good service. Try fun projects . com

1) There is Tom's;

2) James Peterson in the band
P.O. Box 912
Bend, Oregon 97709
541-389-0438 home

3) Fun Projects

[Purdy Swoft]

Originally Posted by marc hildebrant

Purdy,

With regard to the fun products part; while it does regulate the voltage, it doesn't perform the regulation in the same manner as the old three/two unit voltage regulators. The fun product device uses a "shunt" type of voltage regulation while the older voltage regulators devices regulated by reducing the field current to maintain the output voltage constant.

The fun products circuit works, but in a different manner.

Marc

Thanks, how it does it really makes no difference. The fact that it regulates the voltage, is simple to install and holds up well is all that matters to me. The Fun Projects regulator will work just as well for others as it has for me. They are available in six, eight and twelve volt versions and no mods to the original generator is needed, no matter which voltage is used. They can also be had in positive or negative ground version. I've been running our roadster twelve volt positive ground with the original generator for over seven years. One of the good things was , not a single wire had to be changed. The only way a person could know that it was running 12 volt would be if they saw the battery. Oh yeah, it ain't fun products, its Fun Projects. Big difference!

[marc hildebrant]

Purdy,

Thanks for the correction. I'm not sure where I got products from ?

Marc

[Mike V. Florida]

Originally Posted by Purdy Swoft

Actually there are three voltage regulators available for the model A type generator. I use the Fun Projects can style voltage regulator. The Fun Projects regulator fits in place of the cutout and no modifications to the generator is necessary. The regulator looks like the early style cut out but functions like a modern voltage regulator. Fun Projects has a web site. I have used the Fun Projects regulators for years with good service. Try fun projects . com

1) There is Tom's;

2) James Peterson in the band
P.O. Box 912
Bend, Oregon 97709
541-389-0438 home

3) Fun Projects

[Patrick L.]

Mine charges 20 amps at higher speeds and I have no problem. I was initially concerned about this until I read that Tom Andrews recommends the generator be set at 10 amps charge at idle. I do admit for long drives I turn on the headlights if I remember.
__________________
Bill Worden
end quote


I'm going to disagree with you, but, thats OK. You can run your car as you like. A normal 'A' should be set to charge about 3-4 amps at cruise speeds if the lights are not used much. And at 10-12 amps if run at night quite a bit. 20 amps is very hard on these generators, but, again, its your car.

[Purdy Swoft]

Diode cutouts are available that will allow for 20 amp charge, thats if the third brush is pushed all the way down. When useing a diode cutout, I set the third brush as I would if using a cut out. A diode cutout doesn't give voltage regulation, it only allows the generator to charge at the rate that the third brush is set for. In other words if the third brush is set for an 8 amp charge, the amps will increase with rpm until it reaches 8 amps and will remain at that rate unless the rpm drops or more electrical demand is placed on the system. The advantage of a diode cutout is that there are no points to stick and they can be very reliable. Brattons offers a six dollar diode that can easily be installed in an old burned out cutout housing. Snyders has a diode for just over two dollars. they are both different but work equally well. I've used both and you just need a soldering gun and some rosin core solder, instructions included.

[MikeK]

If you show a charge while running and it slams down to -20A when you turn the lights on you have a short to ground in the headlamp wiring. No alternator or voltage regulator will fix that.

Resist the urge to throw new parts at it. Fix the problem, not the symptom.

[A TRUCK]

Originally Posted by MikeK

If you show a charge while running and it slams down to -20A when you turn the lights on you have a short to ground in the headlamp wiring. No alternator or voltage regulator will fix that.

Resist the urge to throw new parts at it. Fix the problem, not the symptom.

___________________________

Thank you for your reply MikeK

Ok, will check the headlamp wiring out - just wanted to add that the ammeter also slams down to -20 when I apply the brakes as well.

[Jim/GA]

Sponsored Links (Register now to hide all advertisements)

Originally Posted by A TRUCK

___________________________

Thank you for your reply MikeK

Ok, will check the headlamp wiring out - just wanted to add that the ammeter also slams down to -20 when I apply the brakes as well.

This is not a good sign. It is not normal. However, it might be an indication of a bad ammeter (reporting much higher current is flowing than is actually flowing).

You would want to compare it to a known good ammeter to rule that out. then start looking for sources of excessive current draw.