Alternator Always Charging

[kippmw]

Hi all. Drove my coupe accross town the other day, probably 50-60 miles total. Even after driving for a while at speed, the ammeter sat at a consistent 9-10 amps charge. It jumped up to 15- 20 amps after cold start, ammeter still sits at 0 when engine is off.. Tested the voltage at the alternator output and the battery while running and got about 7.5 volts, so around expected. The battery seems to be fine...starts the car reliably. Battery didn't seem to be overcharged when I got home. Thoughts? Bad regulator in the alternator?

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[Big hammer]

Clean battery terminals and ground connection, if that doesn't help load check battery

[Bob-A]

Try a different amp gauge. I've had problems with amp gauges lately that have driven me crazy! Latest bad one was made in the USA too.


Bob-A

[ArtimusGordon]

You have a electrical problem. I would disconnect the light switch from the steering column and start the engine and see if the problem is still there. If it is then you can trouble shoot with a multimeter.

[nkaminar]

Hook up a voltage meter in addition to your ammeter. Voltage should be at 7 to 7.5 volts while driving. The battery should be recharged within 5 miles or so and the ammeter going to 0 while driving.

Something is using amps. Either a load on the battery side of the ammeter or the battery is not accepting a charge. How is the water level? How old is the battery? Is the battery warm when you get home? Check to see if the ignition or some other load is on the battery side of the junction box. Or, as you say, could be a bad regulator internal to the alternator.

[kippmw]

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Originally Posted by Big hammer

Clean battery terminals and ground connection, if that doesn't help load check battery

I'll check the grounds.. The battery seems fine, though. The car can sit for weeks and start right up.

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[kippmw]

Originally Posted by Bob-A

Try a different amp gauge. I've had problems with amp gauges lately that have driven me crazy! Latest bad one was made in the USA too.


Bob-A

I've heard about bad repops being unreliable. However, I think this is an original that's been on there since 1971 when my dad and grandpa restored the car. No problems with the gauge in those years.

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[kippmw]

Originally Posted by ArtimusGordon

You have a electrical problem. I would disconnect the light switch from the steering column and start the engine and see if the problem is still there. If it is then you can trouble shoot with a multimeter.

I tried unhooking lights and horn...no effect I'm afraid.

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[kippmw]

Originally Posted by nkaminar

Hook up a voltage meter in addition to your ammeter. Voltage should be at 7 to 7.5 volts while driving. The battery should be recharged within 5 miles or so and the ammeter going to 0 while driving.

Something is using amps. Either a load on the battery side of the ammeter or the battery is not accepting a charge. How is the water level? How old is the battery? Is the battery warm when you get home? Check to see if the ignition or some other load is on the battery side of the junction box. Or, as you say, could be a bad regulator internal to the alternator.

Thanks. I already checked the voltage at running RPM and it all seems fine. If there was a draw on the battery, it wouldn't start after weeks sitting, but it does.

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[Tom Endy]

The battery may be starting to fail. It sounds like the battery is not fully charging up. The regulator in the alternator sees that and tries to charge it up by sending current to it. Check the specific gravity of the battery. I think the tool is called a hydrometer.

Tom Endy

[bbrocksr]

Originally Posted by kippmw

Hi all. Drove my coupe accross town the other day, probably 50-60 miles total. Even after driving for a while at speed, the ammeter sat at a consistent 9-10 amps charge. It jumped up to 15- 20 amps after cold start, ammeter still sits at 0 when engine is off.. Tested the voltage at the alternator output and the battery while running and got about 7.5 volts, so around expected. The battery seems to be fine...starts the car reliably. Battery didn't seem to be overcharged when I got home. Thoughts? Bad regulator in the alternator?

Sent from my SM-G973U using Tapatalk

Alternators are not designed to go to zero, when the battery is fully charged and there is no demand it will go to its minimum output which is 2 or 3 amps . any draw on the system or if the battery is a little weak will cause the output to increase.
Like was stated above, check connections and grounds.
Check battery voltage after it has set overnight.
Turn lights on and off while running to see if the regulator is calling for more output. Regulator is probably ok.
Bill

[nkaminar]

How long has this been going on? Is it a recent problem?

[rotorwrench]

Check all connections, not just grounds. I've seen terminal boxes fried to a crisp due to loose terminals inside. Loose connections create resistance and resistance creates heat. The only continuous loads on a model A are the lights and the coil. The coil will take around 4 amps in operation but it will only draw current when the points are closed so it goes on and off very rapidly. The battery can have deteriorating internal cell connections which can also cause resistance. See if the battery is warmer than normal after driving for a while. It should not get too hot. The coil shouldn't be overly warm either if it is functioning well.

A person can do current draw checks with the car shut down by watching the amp meter when you turn the lights on. The current draw should show on the amp meter as a discharge but go back to zero when the lights are off. This can be as high as 10-amps draw or more depending on light equipment configuration. If you turn on the ignition and the points are closed, there will be a current draw there too and it should be about 4-amps. If the points are open then there should be no draw at all.

Alternators regulate voltage & current depending on the needs of the battery since it helps carry the load. Once the alternator is on line during operation, there should be very little amount of current flow from the alternator to the battery after it reaches a fully charged state. It should only show a small amount of needle movement on a 20-amp meter but it will always show something toward the charge side.

[Badpuppy]

Ammeter is connected only between generator/alternator and battery. Horn and lights have no influence on it. Early models also had the coil connected on the battery side, but that adds only about 4 amps to the reading. FSB 11/29 moved the coil wire to the generator side of the terminal block on all cars, so the coil shouldn't register either.

Ammeters don't often fail, but I suppose it's possible. I would suspect the battery, although it seems good. Easiest part to throw at it, though pricey. But you could let the dog sleep for a while unless you find some kind of short-to-ground between the ammeter and battery, which could be dangerous.

[Ruth]

Originally Posted by Badpuppy

Ammeter is connected only between generator/alternator and battery. Horn and lights have no influence on it.

Not sure I agree with that. When I turn on my lights I definitely see an "influence" on my ammeter.

[katy]

How old is the battery?

[Fhane]

If you are victim of a sulfated battery, you will begin to notice the signs decreasing efficiency. The most common sign of a sulfated battery is one that will not charge very well, or simply refuses to charge at all. If you suspect your electronic accessories are not receiving enough amperage (weak a/c, dim headlights) it is a strong sign that your battery is sulfated. If your battery goes dead long before you expect it to, then there’s a good chance it is a result of sulfation. You can test the battery’s standing voltage with a multi-meter. Any less than 6.3 volts means your battery is undercharged, possibly as a result of sulfation. It is also a possibility to conduct a visual sulfation diagnostic test on your battery’s cells. This will require opening your battery, so it is advised to do this on a covered surface, in a well ventilated area. Carefully remove the caps on the battery top with a flat head screwdriver. You should be able to look inside each hole and get a view of the battery cells, separators, and electrolytes level. A typical sulfated battery will have cells and separators which are gray, grimy, and hard to distinguish from each other. In a healthy battery, the silver lead cells will be clean and clearly distinguished from the black separators.

[Patrick L.]

It could be a bad battery, but, I'm thinking regulator. Its easily replaced.

[eagle]

The ammeters are usually not very accurate. First off, put am inline calibrated ammeter in the circuit and see if the car ammeter is telling the truth. If it is the battery, you should notice a slow crank.

[kippmw]

Thanks all. I should mention that it's a 10 year old alternator and an original ammeter that's been in the car for 50 years (since my dad and grandpa first restored the car). I really doubt that the ammeter is bad. This is a new problem. It could very well be the battery or something drawing on the battery. I'll start there and let you all know. Thanks again!

[MikeK]

The correct generator/alternator voltage for a wet cell vehicle battery is 7.15V, +or- 0.05V. This was the factory set point for generator regulators that came after the A era. Most old repair manuals for all generator era cars call for adjusting cleaned and repaired mechanical regulators to that range.

All of the aftermarket one-wire alternator regulators are set for an extremely high 7.5 or (gasp) higher output. This is done for several reasons:

1) The assumption is a car that is driven once a week or less, maybe for an hour, with a battery that has sat and discharged somewhat, and likely less than perfect electrical connections. You get an extremely high charge rate and fast recovery within that single hour of drive time.

Disadvantage: If all your connections are excellent, you drive more than an hour a week, and you start with a fully charged battery you are instantly boiling/outgassing/overcharging/damaging your battery. Think about it- 7.5V on a 6V battery is the same as a whopping too-high 15.0V on a later 12V battery.

2) The bean-counters victory.- "Wow, my lights sure are bright with the new alternator!"
Yep, that 7.5V+ set-point sells 'em fast.

Disadvantage: A bulb marked 6-8V that lasts 300 hours on 6V lasts maybe 50 on 8V. @7.5V, maybe 75 hours. Try 15V on your 12V modern wheels and see how many bulbs you go through!

Unfortunately there are NO correct 7.15V regulators for the popular 10/12SI one-wire alternators. Additionally those repop regulators have no soft-start. Instead they deliver a whopping (to my oscilloscope and your vehicle electronics) start up square edged surge. There is also no time or temperature compensation to adjust and taper the set point as the vehicle runs and warms under-hood, and the inital starting discharge is recovered. Modern alternators do these things, but not antique 10SI's with one wire conversions.

It is possible to open up a Transpo 6V one-wire 10SI regulator and change the internal voltage-divider resistor array that controls the rotor current drive transistor to give you a more realistic 7.1V set-point, but that is not a do-it-yourself job for the average car enthusiast.

[Badpuppy]

Originally Posted by Ruth

Not sure I agree with that. When I turn on my lights I definitely see an "influence" on my ammeter.

You see the drain from the battery that the generator is not providing. I could have worded that better, I suppose.

Turn up the generator for night driving to keep the battery charged.

[Badpuppy]

To MikeK's point - optimum battery charge voltage is 7.2 -7.9 volts for a 6V battery, twice that for 12V (14.4 - 15.8). Most regulators are set near the midpoint, 7.4 & 14.8, for fast charging with no boilout.

[MikeK]

Originally Posted by Badpuppy

To MikeK's point - optimum battery charge voltage is 7.2 -7.9 volts for a 6V battery, twice that for 12V (14.4 - 15.8). Most regulators are set near the midpoint, 7.4 & 14.8, for fast charging with no boilout.

I would respectfully disagree with that completely. The voltage ranges you spec apply to independent external chargers, not factory spec mechanical generator regulators or integrated regulation multi-wire alternators as originally factory installed.

If left on for extended time or frequently applied to an already fully charged battery those charger set points you list WILL take their toll on a battery.

The regulators set with set-points you list are one-wire jobs or cheap replacements that lack temperature and time compensation that will reduce the initial set voltage significantly, generally in less than 20 minutes of operation. Those replacement aftermarket regulators also lose or lack the ability to remotely sense voltage, usually at a major junction point far from the device output terminal.

[Badpuppy]

Thanks for the info, Mike. But I'm not aware of any time/temperature circuits in any automotive regulators I've seen. The original GM 10Si, for example, has a single set point, a remote sense terminal and an ignition terminal. A steady charge voltage conducts less current as battery charge builds up, so there should be no reason to change it over time.

[nkaminar]

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Alternators on cruising sail boats put out more than 65 amps. They are controlled by sophisticated charge controllers (regulator). They have a complicated charge cycle as shown below. They also have a temperature sensor that is attached to one terminal of the battery to adjust the charge voltage.

[Badpuppy]

Originally Posted by nkaminar

Alternators on cruising sail boats put out more than 65 amps. They are controlled by sophisticated charge controllers (regulator). They have a complicated charge cycle as shown below. They also have a temperature sensor that is attached to one terminal of the battery to adjust the charge voltage.

Thanks for that. Looks similar to modern battery tenders. But I've never seen anything like that on a car. Maybe too modern for me. Learn something new every day.

[Patrick L.]

From what I remember of old Delco internal regulators there was nothing fancy about them.
I'm still thinking the issue is a bad regulator. It could have easily/cheaply been changed awhile ago. Then we'd know if it fixed it or not. I don't know if his alternator would have the 'D' slot for full fielding or not. Some early ones didn't.

Some of these threads certainly take on an interesting life of their own.

[vangorde]

It sounds like a battery or a corroded connection issue.

[rotorwrench]

MikeK has a point about these types of 1-wire conversion alternator. On the GM/Delco 10si type alternators, the rectifier is changed to get the 6-volts needed and has a jumper to the regulator module and the brush holder stack. These alternators may be one wire now but they were never designed to be that. They have the plug with the 2-male spade terminals that were used in the original OEM installations for the alternator warning light and the system voltage sense. Model As and tractors don't use this stuff but that doesn't mean that they couldn't. It's just that it is not considered important by the producers of this equipment. If these two circuits were set up (making it a 3-wire system), it may help with the output of these type units. That voltage sense wire was pretty important to the way the internal regulator works. Since the regulator doesn't know what the battery voltage is, it just has to put out a constant default voltage for it to work.

The alternator has to be pulled apart and a conversion regulator set up purchased to supply the parts for replacement but it can be done by most DIY guys.

[Badpuppy]

Originally Posted by nkaminar

Alternators on cruising sail boats put out more than 65 amps. They are controlled by sophisticated charge controllers (regulator). They have a complicated charge cycle as shown below. They also have a temperature sensor that is attached to one terminal of the battery to adjust the charge voltage.

The light dawns. That charge rate is appropriate to Li-ion batteries. Lead acids are not so finicky. I stand by what I said before.

What powers the alternator on a sailboat?

[katy]

Originally Posted by rotorwrench

the rectifier is changed to get the 6-volts needed.

I assume that you meant regulator, not rectifier?

[nkaminar]

On our sailboat the alternator was on the main engine, a Diesel. Most sailboats are set up that way. We had two huge deep discharge house batteries and a large starting battery. All were flooded lead-acid batteries. The engine was run for an hour once a day to charge up the holding tanks for the refrigerator and freezer. We had solar panels so the alternator was not needed unless the house batteries were run down because of using the inverter or other big loads. The charging curve is designed to charge the lead-acid batteries in the shortest amount of time and to their full capacity. This was years before Li-ion batteries were available. The charge controller for the solar panels had the same charge curve.

The holding tanks for the refrigerator and freezer contained a salt solution that froze and then melted throughout the day to maintain the proper temperatures.

On a sailboat the engine is used to enter an anchorage or to get to a dock at a marina. It is also used to motor when there is no wind or when trying to head directly into the eye of the wind. We motored about half the time. I hated to do it but it was necessary.

[rotorwrench]

Originally Posted by katy

I assume that you meant regulator, not rectifier?

I meant rectifier. Here is a link to a kit on flea-pay.
https://www.ebay.com/itm/10SI-Delco-...6606664?_ul=IN

The kit includes the regulator and brush holder stack with special hardware and the rectifier bridge block. All of this stuff makes for a positive ground polarity, 6-volt alternator. There are even U-tube instructions for these conversions.

It's one way to freshen up an older unit as well since it comes with bearings too.

The best way to use a 10/12si type alternator is as it was originally intended. That is 12-volt 3-wire system but most folks don't want to go 12-volt or negative ground.

[Badpuppy]

Originally Posted by nkaminar

On our sailboat the alternator was on the main engine, a Diesel. Most sailboats are set up that way. We had two huge deep discharge house batteries and a large starting battery. All were flooded lead-acid batteries. The engine was run for an hour once a day to charge up the holding tanks for the refrigerator and freezer. We had solar panels so the alternator was not needed unless the house batteries were run down because of using the inverter or other big loads. The charging curve is designed to charge the lead-acid batteries in the shortest amount of time and to their full capacity. This was years before Li-ion batteries were available. The charge controller for the solar panels had the same charge curve.

The holding tanks for the refrigerator and freezer contained a salt solution that froze and then melted throughout the day to maintain the proper temperatures.

On a sailboat the engine is used to enter an anchorage or to get to a dock at a marina. It is also used to motor when there is no wind or when trying to head directly into the eye of the wind. We motored about half the time. I hated to do it but it was necessary.

OK, I get the picture now, thanks. Pretty elaborate, but apparently more reliable system. Hard to wrench it while standing on the side of the ocean.

Come to learn Model A, learn to be a sailor instead. I'm an inland boy; stays out of the water.