😎 Mighty Wannabe ✅ wrote:
> On 5/13/2023 5:51 PM, Paul in Houston TX wrote:
>> 😎 Mighty Wannabe ✅ wrote:
>>> On 5/13/2023 9:05 AM, Xeno wrote:
>>>> On 13/5/2023 10:11 pm, 😎 Mighty Wannabe ✅ wrote:
>>>>> On 5/13/2023 7:45 AM, Xeno wrote:
>>>>>> On 13/5/2023 9:24 pm, 😎 Mighty Wannabe ✅ wrote:
>>>>>>> On 5/13/2023 7:09 AM, Xeno wrote:
>>>>>>>> On 12/5/2023 2:08 am, Scott Dorsey wrote:
>>>>>>>>> Xeno <xenolith@optusnet.com.au> wrote:
>>>>>>>>>>
>>>>>>>>>> Then it wouldn't be a single wire alternator, would it? Think
>>>>>>>>>> about that
>>>>>>>>>> for a moment. Alternators are, typically, 3 phase. That means
>>>>>>>>>> 3 +ve
>>>>>>>>>> power diodes, 3 -ve power diodes and 3 exciter diodes. If
>>>>>>>>>> there is only
>>>>>>>>>> one output wire, then all *rectification* and control has to
>>>>>>>>>> be on-board.
>>>>>>>>>
>>>>>>>>> When someone says "GM 1-wire alternator" they are talking about
>>>>>>>>> a series
>>>>>>>>> of alternators introduced in 1970 or so, starting with the
>>>>>>>>> Delco 10SI and
>>>>>>>>> including some more modern follow-ons.  These alternators use
>>>>>>>>> internal
>>>>>>>>> rectification and regulation (really just regulating pulses to
>>>>>>>>> the field
>>>>>>>>> coil) and are very, very foolproof.
>>>>>>>>>
>>>>>>>>> Because of this they are frequently retrofitted into older
>>>>>>>>> cars. I see
>>>>>>>>> them on all sorts of older British cars as part of a conversion
>>>>>>>>> to a
>>>>>>>>> modern 12V electrical system.
>>>>>>>>>
>>>>>>>>> There isn't much to go wrong other than having the alternator
>>>>>>>>> go bad.
>>>>>>>>
>>>>>>>> What used to happen to them back in the 70s was that heat and
>>>>>>>> vibration would damage the regulator - even with its
>>>>>>>> encapsulation. A separate regulator mounted on the inner guard
>>>>>>>> or firewall and in the underhood airflow was a much better
>>>>>>>> arrangement.
>>>>>>>>
>>>>>>>
>>>>>>> The OP said it can charge the battery to 13.8V, can't you read?
>>>>>>
>>>>>> The voltage can get to 13.8 *without* pumping much current.
>>>>>> Voltage is *pressure* whereas *current is flow*.
>>>>>>>
>>>>>>>>> Mind you it is possible that the original poster's problem is
>>>>>>>>> that they
>>>>>>>>> have a three-wire alernator or an alternator with external
>>>>>>>>> mechanical
>>>>>>>>> voltage regulator and none of the other wiring is connected.
>>>>>>>>
>>>>>>>> Not enough detail in the OPs post to really know what's what.
>>>>>>>
>>>>>>> I have already provided full explanation. You are too boneheaded
>>>>>>> to understand.
>>>>>>
>>>>>> You have provided proof that you haven't a clue.
>>>>>
>>>>> You don't have the education or practical knowledge to analyze this
>>>>> abnormal situation. You still cannot answer the question why the OP
>>>>> says there is no apparent DC current from the alternator but it can
>>>>> charge the battery to 13.8V when the engine is running.
>>>>>
>>>>> I don't think you can think. Pity.
>>>>
>>>> It has already been mentioned. It's either high resistance
>>>
>>>
>>> If it has high resistance, and connecting after market [DC] ammeter
>>> to the alternator registers cannot detect [DC] current, then it won't
>>> be able to charge the battery to 13.8V and next time the battery
>>> won't have enough juice to crank the motor. Do you have no brain?
>>>
>>>
>>>> or a faulty regulator. I'd be checking connections for resistance
>>>> and continuity before I condemn the regulator. Testing current with
>>>> a load, ie. headlights on, is the usual practice.
>>>
>>> The OP already said there is no detectable [DC] current from the
>>> alternative when the headlights are on. Can't you read?
>>>
>>>> I used to use a large dummy load, to test alternator and generator
>>>> output. I'd also give it a big rev
>>>
>>> The OP already said "No amperage reading even at 2000 rpm". Can't you
>>> read?
>>>
>>> Remainder of your bullshit snipped. Just answer to above question and
>>> you will realize that you are stupid.
>>
>> The op never said that the alt would charge the batt to 13.8v.
>
> Then find your reading glasses and read again.
>
>
>>
>> The op never said what kind of ammeter or voltmeter.
>
>
> The OP said the external ammeter corroborates with the car's dashboard
> ammeter. Can't you read?
>
>
>>
>> A $10 ammeter would likely not show milliamps.
>>
>
> NO car ammeter deals with milliamp. Do you have a brain?
>

You obviously have no knowledge of basic electricity or electronics and
are just a troll.
By the way, there are no germanium power rectifiers.

On 5/14/2023 9:42 PM, Paul in Houston TX wrote:
> 😎 Mighty Wannabe ✅ wrote:
>> On 5/13/2023 5:51 PM, Paul in Houston TX wrote:
>>> 😎 Mighty Wannabe ✅ wrote:
>>>> On 5/13/2023 9:05 AM, Xeno wrote:
>>>>> On 13/5/2023 10:11 pm, 😎 Mighty Wannabe ✅ wrote:
>>>>>> On 5/13/2023 7:45 AM, Xeno wrote:
>>>>>>> On 13/5/2023 9:24 pm, 😎 Mighty Wannabe ✅ wrote:
>>>>>>>> On 5/13/2023 7:09 AM, Xeno wrote:
>>>>>>>>> On 12/5/2023 2:08 am, Scott Dorsey wrote:
>>>>>>>>>> Xeno <xenolith@optusnet.com.au> wrote:
>>>>>>>>>>>
>>>>>>>>>>> Then it wouldn't be a single wire alternator, would it?
>>>>>>>>>>> Think about that
>>>>>>>>>>> for a moment. Alternators are, typically, 3 phase. That
>>>>>>>>>>> means 3 +ve
>>>>>>>>>>> power diodes, 3 -ve power diodes and 3 exciter diodes. If
>>>>>>>>>>> there is only
>>>>>>>>>>> one output wire, then all *rectification* and control has to
>>>>>>>>>>> be on-board.
>>>>>>>>>>
>>>>>>>>>> When someone says "GM 1-wire alternator" they are talking
>>>>>>>>>> about a series
>>>>>>>>>> of alternators introduced in 1970 or so, starting with the
>>>>>>>>>> Delco 10SI and
>>>>>>>>>> including some more modern follow-ons.  These alternators use
>>>>>>>>>> internal
>>>>>>>>>> rectification and regulation (really just regulating pulses
>>>>>>>>>> to the field
>>>>>>>>>> coil) and are very, very foolproof.
>>>>>>>>>>
>>>>>>>>>> Because of this they are frequently retrofitted into older
>>>>>>>>>> cars. I see
>>>>>>>>>> them on all sorts of older British cars as part of a
>>>>>>>>>> conversion to a
>>>>>>>>>> modern 12V electrical system.
>>>>>>>>>>
>>>>>>>>>> There isn't much to go wrong other than having the alternator
>>>>>>>>>> go bad.
>>>>>>>>>
>>>>>>>>> What used to happen to them back in the 70s was that heat and
>>>>>>>>> vibration would damage the regulator - even with its
>>>>>>>>> encapsulation. A separate regulator mounted on the inner guard
>>>>>>>>> or firewall and in the underhood airflow was a much better
>>>>>>>>> arrangement.
>>>>>>>>>
>>>>>>>>
>>>>>>>> The OP said it can charge the battery to 13.8V, can't you read?
>>>>>>>
>>>>>>> The voltage can get to 13.8 *without* pumping much current.
>>>>>>> Voltage is *pressure* whereas *current is flow*.
>>>>>>>>
>>>>>>>>>> Mind you it is possible that the original poster's problem is
>>>>>>>>>> that they
>>>>>>>>>> have a three-wire alernator or an alternator with external
>>>>>>>>>> mechanical
>>>>>>>>>> voltage regulator and none of the other wiring is connected.
>>>>>>>>>
>>>>>>>>> Not enough detail in the OPs post to really know what's what.
>>>>>>>>
>>>>>>>> I have already provided full explanation. You are too
>>>>>>>> boneheaded to understand.
>>>>>>>
>>>>>>> You have provided proof that you haven't a clue.
>>>>>>
>>>>>> You don't have the education or practical knowledge to analyze
>>>>>> this abnormal situation. You still cannot answer the question why
>>>>>> the OP says there is no apparent DC current from the alternator
>>>>>> but it can charge the battery to 13.8V when the engine is running.
>>>>>>
>>>>>> I don't think you can think. Pity.
>>>>>
>>>>> It has already been mentioned. It's either high resistance
>>>>
>>>>
>>>> If it has high resistance, and connecting after market [DC] ammeter
>>>> to the alternator registers cannot detect [DC] current, then it
>>>> won't be able to charge the battery to 13.8V and next time the
>>>> battery won't have enough juice to crank the motor. Do you have no
>>>> brain?
>>>>
>>>>
>>>>> or a faulty regulator. I'd be checking connections for resistance
>>>>> and continuity before I condemn the regulator. Testing current
>>>>> with a load, ie. headlights on, is the usual practice.
>>>>
>>>> The OP already said there is no detectable [DC] current from the
>>>> alternative when the headlights are on. Can't you read?
>>>>
>>>>> I used to use a large dummy load, to test alternator and generator
>>>>> output. I'd also give it a big rev
>>>>
>>>> The OP already said "No amperage reading even at 2000 rpm". Can't
>>>> you read?
>>>>
>>>> Remainder of your bullshit snipped. Just answer to above question
>>>> and you will realize that you are stupid.
>>>
>>> The op never said that the alt would charge the batt to 13.8v.
>>
>> Then find your reading glasses and read again.
>>
>>
>>>
>>> The op never said what kind of ammeter or voltmeter.
>>
>>
>> The OP said the external ammeter corroborates with the car's
>> dashboard ammeter. Can't you read?
>>
>>
>>>
>>> A $10 ammeter would likely not show milliamps.
>>>
>>
>> NO car ammeter deals with milliamp. Do you have a brain?
>>
>
> You obviously have no knowledge of basic electricity or electronics
> and are just a troll.
> By the way, there are no germanium power rectifiers.

Before silicon there were only germanium rectifiers. It was an old car
so most likely the person who modified the car used germanium bridge
rectifier. A germanium rectifier has lower forward voltage, so in high
current application germanium rectifier will consume less power and
generate less heat. That makes it more likely to be used in cars because
of the high current and low 12V battery. Germanium rectifier has higher
reverse leakage current than silicon rectifiers. In this case it
explains perfectly why the OP says the ammeter has negative current flow
when the engine is not running but the key is on.

Apparently you have no imagination to diagnose abnormal situation like
this. The OP says there is no apparent [DC] current from the alternator
but the battery behaves like normal with a rest voltage and a running
voltage. And there is reverse [DC] current when the car is not running
but the key is on.

The reverse current is the current from the battery leaking through the
germanium bridge rectifier back into the alternator coil.

As I have explained in detail in my previous posts in this thread, long
time ago somebody did not fix the alternator problem, and simply used
the AC from the alternator to connect to a germanium bridge rectifier
hidden somewhere inside the dashboard.

By the way, my education background is electrical engineering in university.

On 15/5/2023 12:33 pm, 😎 Mighty Wannabe ✅ wrote:
> On 5/14/2023 9:42 PM, Paul in Houston TX wrote:
>> 😎 Mighty Wannabe ✅ wrote:
>>> On 5/13/2023 5:51 PM, Paul in Houston TX wrote:
>>>> 😎 Mighty Wannabe ✅ wrote:
>>>>> On 5/13/2023 9:05 AM, Xeno wrote:
>>>>>> On 13/5/2023 10:11 pm, 😎 Mighty Wannabe ✅ wrote:
>>>>>>> On 5/13/2023 7:45 AM, Xeno wrote:
>>>>>>>> On 13/5/2023 9:24 pm, 😎 Mighty Wannabe ✅ wrote:
>>>>>>>>> On 5/13/2023 7:09 AM, Xeno wrote:
>>>>>>>>>> On 12/5/2023 2:08 am, Scott Dorsey wrote:
>>>>>>>>>>> Xeno <xenolith@optusnet.com.au> wrote:
>>>>>>>>>>>>
>>>>>>>>>>>> Then it wouldn't be a single wire alternator, would it?
>>>>>>>>>>>> Think about that
>>>>>>>>>>>> for a moment. Alternators are, typically, 3 phase. That
>>>>>>>>>>>> means 3 +ve
>>>>>>>>>>>> power diodes, 3 -ve power diodes and 3 exciter diodes. If
>>>>>>>>>>>> there is only
>>>>>>>>>>>> one output wire, then all *rectification* and control has to
>>>>>>>>>>>> be on-board.
>>>>>>>>>>>
>>>>>>>>>>> When someone says "GM 1-wire alternator" they are talking
>>>>>>>>>>> about a series
>>>>>>>>>>> of alternators introduced in 1970 or so, starting with the
>>>>>>>>>>> Delco 10SI and
>>>>>>>>>>> including some more modern follow-ons.  These alternators use
>>>>>>>>>>> internal
>>>>>>>>>>> rectification and regulation (really just regulating pulses
>>>>>>>>>>> to the field
>>>>>>>>>>> coil) and are very, very foolproof.
>>>>>>>>>>>
>>>>>>>>>>> Because of this they are frequently retrofitted into older
>>>>>>>>>>> cars. I see
>>>>>>>>>>> them on all sorts of older British cars as part of a
>>>>>>>>>>> conversion to a
>>>>>>>>>>> modern 12V electrical system.
>>>>>>>>>>>
>>>>>>>>>>> There isn't much to go wrong other than having the alternator
>>>>>>>>>>> go bad.
>>>>>>>>>>
>>>>>>>>>> What used to happen to them back in the 70s was that heat and
>>>>>>>>>> vibration would damage the regulator - even with its
>>>>>>>>>> encapsulation. A separate regulator mounted on the inner guard
>>>>>>>>>> or firewall and in the underhood airflow was a much better
>>>>>>>>>> arrangement.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> The OP said it can charge the battery to 13.8V, can't you read?
>>>>>>>>
>>>>>>>> The voltage can get to 13.8 *without* pumping much current.
>>>>>>>> Voltage is *pressure* whereas *current is flow*.
>>>>>>>>>
>>>>>>>>>>> Mind you it is possible that the original poster's problem is
>>>>>>>>>>> that they
>>>>>>>>>>> have a three-wire alernator or an alternator with external
>>>>>>>>>>> mechanical
>>>>>>>>>>> voltage regulator and none of the other wiring is connected.
>>>>>>>>>>
>>>>>>>>>> Not enough detail in the OPs post to really know what's what.
>>>>>>>>>
>>>>>>>>> I have already provided full explanation. You are too
>>>>>>>>> boneheaded to understand.
>>>>>>>>
>>>>>>>> You have provided proof that you haven't a clue.
>>>>>>>
>>>>>>> You don't have the education or practical knowledge to analyze
>>>>>>> this abnormal situation. You still cannot answer the question why
>>>>>>> the OP says there is no apparent DC current from the alternator
>>>>>>> but it can charge the battery to 13.8V when the engine is running.
>>>>>>>
>>>>>>> I don't think you can think. Pity.
>>>>>>
>>>>>> It has already been mentioned. It's either high resistance
>>>>>
>>>>>
>>>>> If it has high resistance, and connecting after market [DC] ammeter
>>>>> to the alternator registers cannot detect [DC] current, then it
>>>>> won't be able to charge the battery to 13.8V and next time the
>>>>> battery won't have enough juice to crank the motor. Do you have no
>>>>> brain?
>>>>>
>>>>>
>>>>>> or a faulty regulator. I'd be checking connections for resistance
>>>>>> and continuity before I condemn the regulator. Testing current
>>>>>> with a load, ie. headlights on, is the usual practice.
>>>>>
>>>>> The OP already said there is no detectable [DC] current from the
>>>>> alternative when the headlights are on. Can't you read?
>>>>>
>>>>>> I used to use a large dummy load, to test alternator and generator
>>>>>> output. I'd also give it a big rev
>>>>>
>>>>> The OP already said "No amperage reading even at 2000 rpm". Can't
>>>>> you read?
>>>>>
>>>>> Remainder of your bullshit snipped. Just answer to above question
>>>>> and you will realize that you are stupid.
>>>>
>>>> The op never said that the alt would charge the batt to 13.8v.
>>>
>>> Then find your reading glasses and read again.
>>>
>>>
>>>>
>>>> The op never said what kind of ammeter or voltmeter.
>>>
>>>
>>> The OP said the external ammeter corroborates with the car's
>>> dashboard ammeter. Can't you read?
>>>
>>>
>>>>
>>>> A $10 ammeter would likely not show milliamps.
>>>>
>>>
>>> NO car ammeter deals with milliamp. Do you have a brain?
>>>
>>
>> You obviously have no knowledge of basic electricity or electronics
>> and are just a troll.
>> By the way, there are no germanium power rectifiers.
>
> Before silicon there were only germanium rectifiers. It was an old car
> so most likely the person who modified the car used germanium bridge
> rectifier. A germanium rectifier has lower forward voltage, so in high
> current application germanium rectifier will consume less power and
> generate less heat. That makes it more likely to be used in cars because
> of the high current and low 12V battery. Germanium rectifier has higher
> reverse leakage current than silicon rectifiers. In this case it
> explains perfectly why the OP says the ammeter has negative current flow
> when the engine is not running but the key is on.
>
> Apparently you have no imagination to diagnose abnormal situation like
>
I hate to break this to you but *imagination* plays no role in
diagnosis. We mechanics deal with the *facts* of any situation.

this. The OP says there is no apparent [DC] current from the alternator
> but the battery behaves like normal with a rest voltage and a running
> voltage. And there is reverse [DC] current when the car is not running
> but the key is on. >
> The reverse current is the current from the battery leaking through the
> germanium bridge rectifier back into the alternator coil.
>
> As I have explained in detail in my previous posts in this thread, long
> time ago somebody did not fix the alternator problem, and simply used
> the AC from the alternator to connect to a germanium bridge rectifier
> hidden somewhere inside the dashboard.
>
> By the way, my education background is electrical engineering in
> university.

1948 Pontiac, 12V battery, one wire alternator (was working when parked 12 years ago).
No amperage reading even at 2000 rpm. Battery voltage 12.6V. Battery voltage with car running 13.8V, however amp meter only reads 0 or negative with headlights on. Placed an after market ammeter between the alternator and the battery. Same reading as ammeter in the dash.
How could this be? Alternator supplies voltage but no current.
After idle for 12 years maybe residual magnetism is gone. Needs to be excited. Can't find a YouTube that shows me which terminals to zap.
All help is appreciated. I can certainly buy a new unit, but possibly have other problems.

Thank you

On 5/8/2023 23:58, Ivan Vegvary wrote:
> 1948 Pontiac, 12V battery, one wire alternator (was working when
> parked 12 years ago). No amperage reading even at 2000 rpm. Battery
> voltage 12.6V. Battery voltage with car running 13.8V, however amp
> meter only reads 0 or negative with headlights on. Placed an after
> market ammeter between the alternator and the battery. Same reading
> as ammeter in the dash. How could this be? Alternator supplies
> voltage but no current. After idle for 12 years maybe residual
> magnetism is gone. Needs to be excited. Can't find a YouTube that
> shows me which terminals to zap. All help is appreciated. I can
> certainly buy a new unit, but possibly have other problems.
>
> Thank you

That's a tough one... if it's been sitting for 12 years, you've got to
start with the basics. Have you cleaned all of the grounds? Is the
terminal for the wire on the alternator clean? In 1948, it would have
been a 6 volt positive ground system. I'm assuming that someone has
since converted the car to 12 volt negative ground.

On 5/8/2023 11:58 PM, Ivan Vegvary wrote:
> 1948 Pontiac, 12V battery, one wire alternator (was working when parked 12 years ago).
> No amperage reading even at 2000 rpm. Battery voltage 12.6V. Battery voltage with car running 13.8V, however amp meter only reads 0 or negative with headlights on. Placed an after market ammeter between the alternator and the battery. Same reading as ammeter in the dash.
> How could this be? Alternator supplies voltage but no current.
> After idle for 12 years maybe residual magnetism is gone. Needs to be excited. Can't find a YouTube that shows me which terminals to zap.
> All help is appreciated. I can certainly buy a new unit, but possibly have other problems.
>
> Thank you

If you get 13.8V when the car is running, that means the alternator is
providing output.

The alternator output is AC. You need to use AC ammeter to measure the
AC current output from the alternator.

On 9/5/2023 11:34 pm, 😎 Mighty Wannabe ✅ wrote:
> On 5/8/2023 11:58 PM, Ivan Vegvary wrote:
>> 1948 Pontiac, 12V battery, one wire alternator (was working when
>> parked 12 years ago).
>> No amperage reading even at 2000 rpm.  Battery voltage 12.6V.  Battery
>> voltage with car running 13.8V, however amp meter only reads 0 or
>> negative with headlights on.  Placed an after market ammeter between
>> the alternator and the battery.  Same reading as ammeter in the dash.
>> How could this be?  Alternator supplies voltage but no current.
>> After idle for 12 years maybe residual magnetism is gone.  Needs to be
>> excited.  Can't find a YouTube that shows me which terminals to zap.
>> All help is appreciated.  I can certainly buy a new unit, but possibly
>> have other problems.
>>
>> Thank you
>
> If you get 13.8V when the car is running, that means the alternator is
> providing output.
>
> The alternator output is AC. You need to use AC ammeter to measure the
> AC current output from the alternator.
>
Correction, the alternator output is DC. The 6 internal power diodes
provide the necessary rectification. The 3 exciter diodes are meant to
excite the field coils and set the generation process into gear.

--
Xeno

Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

On 5/9/2023 10:39 AM, Xeno wrote:
> On 9/5/2023 11:34 pm, 😎 Mighty Wannabe ✅ wrote:
>> On 5/8/2023 11:58 PM, Ivan Vegvary wrote:
>>> 1948 Pontiac, 12V battery, one wire alternator (was working when
>>> parked 12 years ago).
>>> No amperage reading even at 2000 rpm.  Battery voltage 12.6V.
>>> Battery voltage with car running 13.8V, however amp meter only reads
>>> 0 or negative with headlights on.  Placed an after market ammeter
>>> between the alternator and the battery.  Same reading as ammeter in
>>> the dash.
>>> How could this be?  Alternator supplies voltage but no current.
>>> After idle for 12 years maybe residual magnetism is gone. Needs to
>>> be excited.  Can't find a YouTube that shows me which terminals to zap.
>>> All help is appreciated.  I can certainly buy a new unit, but
>>> possibly have other problems.
>>>
>>> Thank you
>>
>> If you get 13.8V when the car is running, that means the alternator
>> is providing output.
>>
>> The alternator output is AC. You need to use AC ammeter to measure
>> the AC current output from the alternator.
>>
> Correction, the alternator output is DC. The 6 internal power diodes
> provide the necessary rectification. The 3 exciter diodes are meant to
> excite the field coils and set the generation process into gear.
>

Are you sure that's true for 1948 Pontiac?

Maybe that alternator had been modified to use external rectifiers and
regulator.

Ivan Vegvary wrote:
> 1948 Pontiac, 12V battery, one wire alternator (was working when parked 12 years ago).
> No amperage reading even at 2000 rpm. Battery voltage 12.6V. Battery voltage with car running 13.8V, however amp meter only reads 0 or negative with headlights on. Placed an after market ammeter between the alternator and the battery. Same reading as ammeter in the dash.
> How could this be? Alternator supplies voltage but no current.
> After idle for 12 years maybe residual magnetism is gone. Needs to be excited. Can't find a YouTube that shows me which terminals to zap.
> All help is appreciated. I can certainly buy a new unit, but possibly have other problems.
>
> Thank you

There must be current... but not a whole lot.
Possible corrosion... some where.
the alternator wire at alt or batt.
alt slip rings corroded.
alt brushes stuck.
internal corrosion at the diode plates.
bad alt ground.

On Tuesday, May 9, 2023 at 3:45:10 PM UTC-7, Paul in Houston TX wrote:
> Ivan Vegvary wrote:
> > 1948 Pontiac, 12V battery, one wire alternator (was working when parked 12 years ago).
> > No amperage reading even at 2000 rpm. Battery voltage 12.6V. Battery voltage with car running 13.8V, however amp meter only reads 0 or negative with headlights on. Placed an after market ammeter between the alternator and the battery. Same reading as ammeter in the dash.
> > How could this be? Alternator supplies voltage but no current.
> > After idle for 12 years maybe residual magnetism is gone. Needs to be excited. Can't find a YouTube that shows me which terminals to zap.
> > All help is appreciated. I can certainly buy a new unit, but possibly have other problems.
> >
> > Thank you
> There must be current... but not a whole lot.
> Possible corrosion... some where.
> the alternator wire at alt or batt.
> alt slip rings corroded.
> alt brushes stuck.
> internal corrosion at the diode plates.
> bad alt ground.
Thanks all of you for your thoughtful responses. Will check and clean all connections.

On 10/5/2023 3:05 am, 😎 Mighty Wannabe ✅ wrote:
> On 5/9/2023 10:39 AM, Xeno wrote:
>> On 9/5/2023 11:34 pm, 😎 Mighty Wannabe ✅ wrote:
>>> On 5/8/2023 11:58 PM, Ivan Vegvary wrote:
>>>> 1948 Pontiac, 12V battery, one wire alternator (was working when
>>>> parked 12 years ago).
>>>> No amperage reading even at 2000 rpm.  Battery voltage 12.6V.
>>>> Battery voltage with car running 13.8V, however amp meter only reads
>>>> 0 or negative with headlights on.  Placed an after market ammeter
>>>> between the alternator and the battery.  Same reading as ammeter in
>>>> the dash.
>>>> How could this be?  Alternator supplies voltage but no current.
>>>> After idle for 12 years maybe residual magnetism is gone. Needs to
>>>> be excited.  Can't find a YouTube that shows me which terminals to zap.
>>>> All help is appreciated.  I can certainly buy a new unit, but
>>>> possibly have other problems.
>>>>
>>>> Thank you
>>>
>>> If you get 13.8V when the car is running, that means the alternator
>>> is providing output.
>>>
>>> The alternator output is AC. You need to use AC ammeter to measure
>>> the AC current output from the alternator.
>>>
>> Correction, the alternator output is DC. The 6 internal power diodes
>> provide the necessary rectification. The 3 exciter diodes are meant to
>> excite the field coils and set the generation process into gear.
>>
>
>
> Are you sure that's true for 1948 Pontiac?
>
> Maybe that alternator had been modified to use external rectifiers and
> regulator.
>
Then it wouldn't be a single wire alternator, would it? Think about that
for a moment. Alternators are, typically, 3 phase. That means 3 +ve
power diodes, 3 -ve power diodes and 3 exciter diodes. If there is only
one output wire, then all *rectification* and control has to be on-board.

--
Xeno

Nothing astonishes Noddy so much as common sense and plain dealing.
(with apologies to Ralph Waldo Emerson)

On 5/10/2023 12:55 AM, Xeno wrote:
> On 10/5/2023 3:05 am, 😎 Mighty Wannabe ✅ wrote:
>> On 5/9/2023 10:39 AM, Xeno wrote:
>>> On 9/5/2023 11:34 pm, 😎 Mighty Wannabe ✅ wrote:
>>>> On 5/8/2023 11:58 PM, Ivan Vegvary wrote:
>>>>> 1948 Pontiac, 12V battery, one wire alternator (was working when
>>>>> parked 12 years ago).
>>>>> No amperage reading even at 2000 rpm.  Battery voltage 12.6V.
>>>>> Battery voltage with car running 13.8V, however amp meter only
>>>>> reads 0 or negative with headlights on.  Placed an after market
>>>>> ammeter between the alternator and the battery.  Same reading as
>>>>> ammeter in the dash.
>>>>> How could this be?  Alternator supplies voltage but no current.
>>>>> After idle for 12 years maybe residual magnetism is gone. Needs to
>>>>> be excited.  Can't find a YouTube that shows me which terminals to
>>>>> zap.
>>>>> All help is appreciated.  I can certainly buy a new unit, but
>>>>> possibly have other problems.
>>>>>
>>>>> Thank you
>>>>
>>>> If you get 13.8V when the car is running, that means the alternator
>>>> is providing output.
>>>>
>>>> The alternator output is AC. You need to use AC ammeter to measure
>>>> the AC current output from the alternator.
>>>>
>>> Correction, the alternator output is DC. The 6 internal power diodes
>>> provide the necessary rectification. The 3 exciter diodes are meant
>>> to excite the field coils and set the generation process into gear.
>>>
>>
>>
>> Are you sure that's true for 1948 Pontiac?
>>
>> Maybe that alternator had been modified to use external rectifiers
>> and regulator.
>>
> Then it wouldn't be a single wire alternator, would it? Think about
> that for a moment. Alternators are, typically, 3 phase. That means 3
> +ve power diodes, 3 -ve power diodes and 3 exciter diodes. If there is
> only one output wire, then all *rectification* and control has to be
> on-board.
>

If the alternator really has DC output, then the car's ammeter and
external ammeter should register DC current.

I believe somehow the alternator burnt the internal diodes, and the
owner rewired it as single phase output and used external rectifier
after the car's dashboard ammeter. That means the dashboard ammeter has
not been working properly ever since. A germanium diode was used so some
reverse current is flowing back into the alternator when the engine is
not running but the key is on auxiliary. That's when and why the
dashboard ammeter registers negative.

On 5/10/2023 9:39 AM, 😎 Mighty Wannabe ✅ wrote:
> On 5/10/2023 12:55 AM, Xeno wrote:
>> On 10/5/2023 3:05 am, 😎 Mighty Wannabe ✅ wrote:
>>> On 5/9/2023 10:39 AM, Xeno wrote:
>>>> On 9/5/2023 11:34 pm, 😎 Mighty Wannabe ✅ wrote:
>>>>> On 5/8/2023 11:58 PM, Ivan Vegvary wrote:
>>>>>> 1948 Pontiac, 12V battery, one wire alternator (was working when
>>>>>> parked 12 years ago).
>>>>>> No amperage reading even at 2000 rpm.  Battery voltage 12.6V.
>>>>>> Battery voltage with car running 13.8V, however amp meter only
>>>>>> reads 0 or negative with headlights on. Placed an after market
>>>>>> ammeter between the alternator and the battery.  Same reading as
>>>>>> ammeter in the dash.
>>>>>> How could this be?  Alternator supplies voltage but no current.
>>>>>> After idle for 12 years maybe residual magnetism is gone. Needs
>>>>>> to be excited.  Can't find a YouTube that shows me which
>>>>>> terminals to zap.
>>>>>> All help is appreciated.  I can certainly buy a new unit, but
>>>>>> possibly have other problems.
>>>>>>
>>>>>> Thank you
>>>>>
>>>>> If you get 13.8V when the car is running, that means the
>>>>> alternator is providing output.
>>>>>
>>>>> The alternator output is AC. You need to use AC ammeter to measure
>>>>> the AC current output from the alternator.
>>>>>
>>>> Correction, the alternator output is DC. The 6 internal power
>>>> diodes provide the necessary rectification. The 3 exciter diodes
>>>> are meant to excite the field coils and set the generation process
>>>> into gear.
>>>>
>>>
>>>
>>> Are you sure that's true for 1948 Pontiac?
>>>
>>> Maybe that alternator had been modified to use external rectifiers
>>> and regulator.
>>>
>> Then it wouldn't be a single wire alternator, would it? Think about
>> that for a moment. Alternators are, typically, 3 phase. That means 3
>> +ve power diodes, 3 -ve power diodes and 3 exciter diodes. If there
>> is only one output wire, then all *rectification* and control has to
>> be on-board.
>>
>
> If the alternator really has DC output, then the car's [DC] ammeter
> and external [DC] ammeter should register DC current.
>
> I believe somehow the alternator burnt the internal diodes, and the
> owner rewired it as single phase [AC] output and used external [bridge
> rectifier] after the car's dashboard [DC] ammeter. That means the
> dashboard [DC] ammeter has not been working properly ever since
> [because it was AC coming from the alternator]. A germanium [bridge
> rectifier] was used so some reverse current is flowing back into the
> alternator when the engine is not running but the key is on auxiliary.
> That's when and why the dashboard ammeter registers negative.
>

I've some made minor corrections in square brackets [    ] above to
clarify my points.

I think I have the correct line of thinking.