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Old 06-14-2021, 06:40 PM   #1
kippmw
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Default Alternator Always Charging

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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Old 06-14-2021, 06:56 PM   #2
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Default Re: Alternator Always Charging

Clean battery terminals and ground connection, if that doesn't help load check battery
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Old 06-14-2021, 07:19 PM   #3
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Smile Re: Alternator Always Charging

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.


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Old 06-14-2021, 07:36 PM   #4
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Default Re: Alternator Always Charging

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.

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Old 06-14-2021, 07:37 PM   #5
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Default Re: Alternator Always Charging

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.
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Old 06-14-2021, 08:23 PM   #6
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Default Re: Alternator Always Charging

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Quote:
Originally Posted by Big hammer View Post
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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Old 06-14-2021, 08:26 PM   #7
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Default Re: Alternator Always Charging

Quote:
Originally Posted by Bob-A View Post
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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Old 06-14-2021, 08:27 PM   #8
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Default Re: Alternator Always Charging

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Originally Posted by ArtimusGordon View Post
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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Old 06-14-2021, 08:29 PM   #9
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Default Re: Alternator Always Charging

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Originally Posted by nkaminar View Post
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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Old 06-14-2021, 08:53 PM   #10
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Default Re: Alternator Always Charging

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.

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Old 06-14-2021, 08:55 PM   #11
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Default Re: Alternator Always Charging

Quote:
Originally Posted by kippmw View Post
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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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.
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Old 06-15-2021, 06:29 AM   #12
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Default Re: Alternator Always Charging

How long has this been going on? Is it a recent problem?
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Old 06-15-2021, 07:20 AM   #13
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Default Re: Alternator Always Charging

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.
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Old 06-15-2021, 09:17 AM   #14
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Default Re: Alternator Always Charging

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.
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Old 06-15-2021, 09:37 AM   #15
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Default Re: Alternator Always Charging

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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.
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Old 06-15-2021, 10:11 AM   #16
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Default Re: Alternator Always Charging

How old is the battery?
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Old 06-15-2021, 11:26 AM   #17
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Default Re: Alternator Always Charging

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.
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Old 06-15-2021, 04:07 PM   #18
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Default Re: Alternator Always Charging

It could be a bad battery, but, I'm thinking regulator. Its easily replaced.
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Old 06-15-2021, 08:19 PM   #19
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Default Re: Alternator Always Charging

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.
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Old 06-15-2021, 09:06 PM   #20
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Default Re: Alternator Always Charging

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!
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