Curious question on alternators
- Thread starter 37 Coupe
- Start date
Tom Wesenberg
Well-known member
Here's the last "dependable" alternator I had to work on. I've had to do lots of repairs to alternators, including burned slip rings, worn out slip rings and brushes, burned out diode trio's, Burned out field windings, burned out voltage regulators, bad bearings, and burned out diodes. When diodes go bad they can go open and short. A shorted diode sends AC voltage to the battery and that can sure mess up a battery.
This is a 6 volt + ground alternator with a shot slip ring, burned out diodes and burned out regulator, but I've had to fix plenty of modern 12 volt - ground alternators also.
Jordan
Well-known member
who cares? To each is their own. People who run alternators will always say an alternator is more reliable. A person who runs a generator will always say an generator is more reliable. This fight over generators/alternators happens every week and the same people say the same things.
Tom Wesenberg
Well-known member
37 COUPE cares, and I'm sure others are glad to learn the pros and cons of each. Not everyone knows that diodes can short and send AC current to the battery.
Maybe you already knew that, maybe not, or maybe you don't care to learn that, but some others do care.
Maybe you already knew that, maybe not, or maybe you don't care to learn that, but some others do care.
Special Coupe Frank
Well-known member
My '28 Coupe has an alternator ( 6-volt, positive ground ). Came with the car. It works. Car is a driver, far, far, very far from ever being a "show car". Will probably keep the alternator until someone "gives" me a working OEM genny.
That said;
I've been driving old iron ( lets define that as "six-volt") since getting my license over 25 years ago. ( Chevrolet, Ford, De Soto, Chrysler, Plymouth... )
Everything I driven during that period that was originally furnished with a generator, kept its generator. As long as the brushes and wiring were good, "they just worked".
If a vehicle sat un-used for a long period of time ( manys months to a year or more ), the commutator migh oxidize enough that the genny would not charge when the vehicle was started, but that was usually cured by a piece of fine sand-paper held against the commutator with the engine idling.
I have heard some commentary over on the AACA Forum ( which discusses all makes of cars and trucks ), that older generator systems, with the adjustable third-brush, are perhaps more fussy than "modern" generators ( made after about 1940, with two brushes and the three-unit regulator)... but I have no driving experience with third-brush gennys ( I don't think the Ford 9-N from youth counts here, although I don't ever remember having trouble from the generator on that beast.)
Once Detroit settled on the 2-brush generator with the three-unit Voltage - Current -Cut-out Regulators, they became very reliable. The big limitations were current output ( 35 amps was about the max from a 6-volt genny), and no output at low speeds.
I have had an equal amount of grief( which is to say, "not much") over the years from alternator systems too... AND, the FACTORY alternator on my '64 Valiant, as well as my Model A exhibits "flare" when the engine accelerates from idle ( read: voltage / current falls-off when the engine is idling ... so long as the out-put comes-up when I pull away from the stop, that's fine with me....)
If I had a vehicle with a working generator system, I do not think I would replace it with an alternator.
As I said at the top of my post, my Model A came with an alternator, and will probably keep it as long as it keeps working.
That said;
I've been driving old iron ( lets define that as "six-volt") since getting my license over 25 years ago. ( Chevrolet, Ford, De Soto, Chrysler, Plymouth... )
Everything I driven during that period that was originally furnished with a generator, kept its generator. As long as the brushes and wiring were good, "they just worked".
If a vehicle sat un-used for a long period of time ( manys months to a year or more ), the commutator migh oxidize enough that the genny would not charge when the vehicle was started, but that was usually cured by a piece of fine sand-paper held against the commutator with the engine idling.
I have heard some commentary over on the AACA Forum ( which discusses all makes of cars and trucks ), that older generator systems, with the adjustable third-brush, are perhaps more fussy than "modern" generators ( made after about 1940, with two brushes and the three-unit regulator)... but I have no driving experience with third-brush gennys ( I don't think the Ford 9-N from youth counts here, although I don't ever remember having trouble from the generator on that beast.)
Once Detroit settled on the 2-brush generator with the three-unit Voltage - Current -Cut-out Regulators, they became very reliable. The big limitations were current output ( 35 amps was about the max from a 6-volt genny), and no output at low speeds.
I have had an equal amount of grief( which is to say, "not much") over the years from alternator systems too... AND, the FACTORY alternator on my '64 Valiant, as well as my Model A exhibits "flare" when the engine accelerates from idle ( read: voltage / current falls-off when the engine is idling ... so long as the out-put comes-up when I pull away from the stop, that's fine with me....)
If I had a vehicle with a working generator system, I do not think I would replace it with an alternator.
As I said at the top of my post, my Model A came with an alternator, and will probably keep it as long as it keeps working.
Kurt in NJ
Well-known member
Reverse polarity junpstart--
with alternator---smoke, fried alternator
with generator --car starts, generator doesn't charge, worse case --battery polarity gets reversed, generator polarizes itself to new polarity---ammeter works backwards.
The delco alt most commonly used has made much money for rebuilders, they last just long enough, the parts are cheap, they rebuild easy ---they are good for repeat business.
In the automotive electric business many of the employees are several generations distant from the generator era, it is not totally understood, when I started the generator was taken off the car, fixed, the regulator adjusted, when a cae with an alternator proplem was fixed it got a new alternator and regulator, if that didn't fix it the hands were thrown up --another regulator was tried,another alternator ---it was a mystery, now the generator is the mystery, the delco alternator is known--after fixing thousands of them again and again.
I have not touched my gen in 40 years other than to adjust the 3rd brush, nor have I changed the belt or waterpump, have long life from batterys, the vehicle with the delco alt (74 chevy truck) has had the alt off 2 times in the 35 years of my ownership ---to me that makes the generator more reliable.
with alternator---smoke, fried alternator
with generator --car starts, generator doesn't charge, worse case --battery polarity gets reversed, generator polarizes itself to new polarity---ammeter works backwards.
The delco alt most commonly used has made much money for rebuilders, they last just long enough, the parts are cheap, they rebuild easy ---they are good for repeat business.
In the automotive electric business many of the employees are several generations distant from the generator era, it is not totally understood, when I started the generator was taken off the car, fixed, the regulator adjusted, when a cae with an alternator proplem was fixed it got a new alternator and regulator, if that didn't fix it the hands were thrown up --another regulator was tried,another alternator ---it was a mystery, now the generator is the mystery, the delco alternator is known--after fixing thousands of them again and again.
I have not touched my gen in 40 years other than to adjust the 3rd brush, nor have I changed the belt or waterpump, have long life from batterys, the vehicle with the delco alt (74 chevy truck) has had the alt off 2 times in the 35 years of my ownership ---to me that makes the generator more reliable.
steve s
Well-known member
Tom,
I'm wondering if there is ever any warning or way to check for imminent alternator failure? I assume that diode failure is sudden and unpredictable, and I suppose bearing noise can creep in gradually, but what about the other stuff?
Also, while I'm picking your brain, do you know about how much the diode current leakage is? Are we talking about milliamps, microamps, nanoamps ...? Or, are you in the denial camp?
Thanks!
Steve
Peter J
Well-known member
I had sealed beams in my 31 in highschool. When driving at night, I realized I was taking a little more from the batt. than I was giving from the gen. I'd just park it on a little hill. No start? I'd just pop the clutch and I was gone. No diodes to excite. Never gave it a second thought.
Pete
Pete
Tom Wesenberg
Well-known member
As you say, there is usually no warning as the diodes suddenly go open or closed, or the leads come detached from the diode. If the battery stays charged during the day, but gets low or the amp meter shows a discharge during night driving, you likely have one or two burned out diodes. If the ammeter shows too high a charge, the internal voltage regulator is most likely bad.
The back drain would be in the milliamps. My friend uses an alternator on his A and if I have my meter along the next time I see him, I'll measure the drain. If you use a master disconnect switch just leave it open and connect your meter across the switch to measure the drain. Start with the meter on the highest amp setting, then keep switching down until you can get an accurate reading. Since the drain is unknown, this way you won't peg or damage the meter.
Dale Miller
Junior Member
One thing that no one mentioned is that if the batt. is completly dead with an alt. you can not get the car to start by pushing it!! An alt. requires some voltage to it before it will start outputing so if no output there is
no voltage to ingition and no spark = no start!!
no voltage to ingition and no spark = no start!!
Milton
Well-known member
Just when you thought it was settled.
Bill, It is true what Mike V. Florida said about diodes.
It is called reverse leakage current, however, it is only present when the diode is in a reverse bias mode.
And it had how many miles on it? Everything breaks eventually.
Jordan, Deep down inside I think it may be you that cares, otherwise why do you read these mundane posts.
Please consider this as a discussion rather than a fight.
I care, but mostly about balanced discussions. Not everyone knows a cutout can stick and send DC current to the generator which in turn will run down the battery.
Right on Special Coupe Frank! Same here.
True the alternator is a gold mine for rebuilders, clean off the slip rings and install two brushes and down the road. Why it is so simple that I have even done it myself.
The regulator/alternator arguement is more appropriate with generators. Seen it myself, the layman normally went for the regulator because it was cheapest. They wouldn't know about polarizing and it wouldn't work. Go get a generator, hmmm that doesn't work either. Alternators come with the regulator built in.
I have done a generator under in less than a minute compliments of the third brush.
And the Model A has how many miles in those forty years compared to the Chevy in 35? How many rpm? How many accessories each? Hmmmmm. 
Another thing that no one mentions is that if the batt. is completly dead with an alt. the driver needs to learn how to read a voltmeter or ammeter.
Bill, It is true what Mike V. Florida said about diodes.
It is called reverse leakage current, however, it is only present when the diode is in a reverse bias mode.And it had how many miles on it? Everything breaks eventually.
Jordan, Deep down inside I think it may be you that cares, otherwise why do you read these mundane posts.
Please consider this as a discussion rather than a fight. I care, but mostly about balanced discussions. Not everyone knows a cutout can stick and send DC current to the generator which in turn will run down the battery.
Right on Special Coupe Frank! Same here.
True the alternator is a gold mine for rebuilders, clean off the slip rings and install two brushes and down the road. Why it is so simple that I have even done it myself.
The regulator/alternator arguement is more appropriate with generators. Seen it myself, the layman normally went for the regulator because it was cheapest. They wouldn't know about polarizing and it wouldn't work. Go get a generator, hmmm that doesn't work either. Alternators come with the regulator built in.
I have done a generator under in less than a minute compliments of the third brush.
And the Model A has how many miles in those forty years compared to the Chevy in 35? How many rpm? How many accessories each? Hmmmmm. Another thing that no one mentions is that if the batt. is completly dead with an alt. the driver needs to learn how to read a voltmeter or ammeter.
Hi Guys;
THe reason for an alternator is in MHOP is the Generator ,as with the model a ,is a constant amperage is produced regardless of the load and the battery can be cooked. The alternater produces the required amperage and no more. If Henry was alive today he would have installed the alternater!!
Bob F
THe reason for an alternator is in MHOP is the Generator ,as with the model a ,is a constant amperage is produced regardless of the load and the battery can be cooked. The alternater produces the required amperage and no more. If Henry was alive today he would have installed the alternater!!
Bob F
BILL WILLIAMSON
Well-known member
'30 coupe, 6 volt alternator, 6 year old battery, no trickle charger, sat 3 months while I was in the horspistal and fired off like a flame from a "BIC."
hardtimes
Well-known member
Milton,
Nice analytical breakdown....except for BILLs input. Read it again, he simply says that 'setup properly, it won't drain the battery'. IMO he is right and that's how mine is 'setup'..i.e.- alternator in conjunction with a master cutoff switch. Battery has never run down!
Nice analytical breakdown....except for BILLs input. Read it again, he simply says that 'setup properly, it won't drain the battery'. IMO he is right and that's how mine is 'setup'..i.e.- alternator in conjunction with a master cutoff switch. Battery has never run down!
Tom Wesenberg
Well-known member
That's why at least 3 of us make and sell electronic voltage regulators. Makes the generator system slicker than snot on a doorknob!
I've had a 12V one wire GM alternator on my '30 roadster for 25 years-no problems. I've had a 12V FoMoCo generator with separate voltage regulator on my '28 speedster for 5 years-no problems. I had a 6V stock generator with a points type cutout for 15 years then later with a solid state cutout for 10 years on my '30 P/U-no problems. They have all been "VERY DRIVEN" and also "VERY MAINTAINED" automobiles-maybe I've just been lucky.?.? They've all worked for me.
Tom Wesenberg
Well-known member
There you go.......WELL MAINTAINED is the key!!!!!!
I've never had an original cutout stick and I think the main reason one might stick is if the charging system has a bad connection, and the generator doesn't have an electronic voltage regulator, the voltage can go up to 40 volts, and this is what can burn the cutout contacts and blow headlights and taillights.
Milton
Well-known member
I agree with Bills input in post #8, and then;
in his post #11.
Then Bill sez,
in his post #12.
This is the post I commented about when I posted;
Bill, It is true what Mike V. Florida said about diodes.
It is called reverse leakage current, however, it is only present when the diode is in a reverse bias mode. So I took it to mean he (Bill) disagreed about reverse leakage current, which he (Bill) did not. He disagreed that reverse leakage current could run the battery down because it wouldn't affect a properly set up one wire alternator.
Now for the statement at the end of your post. I will alter it a bit to reflect my experience as follows. That's about how mine is, alternator with no master cutoff switch. Battery has never run down!
P.S. I agree with Bill Williamson whole heartedly.
Franchise_24
Well-known member
Explain your electronic voltage regulator please. Do you mean it will auto adjust like for a night time ride to boost the power when you run your headlights so you don't have to adjust the brush for more power? Please go into detail.
Thanks,
Neal
MrTube
Well-known member
I think the only thing I can add to this thread is the ONLY reason the model A came with a DC generator is high current silicon diodes were not available until the 1960s. If they had these in the 1920s-30s you can bet your life every car would have had an alternator.
An alternator is superior in almost every way to a dc generator.
That being said, my opinion is if you want to drive a model A the way it was built you should have a generator and run a 6 volt battery. This just happens to be what I want from a Model A. If you want a steadier output then install one of Tom's regulators, its a good product. The generator on the model A is VERY reliable, it simply has a fairly low output.
If you want cleaner power and a lot more of it you should be running a 12V alternator its a simple as that. Comparing a 7-8 volt generator which can barely burp out 20A to a 14V alternator which can produce 100-150A all day long is simply ridicules.
14v @ 100A = 1400 watts vs 7v @ 20a = 140 watts. Think its really fair or necessary to compare the two?
I ran a Delco 105A alternator on my last vehicle and often drew enough current to drop the system to 12 volts cruising down the highway. The alternator survived for many years with no problem. Sure you can pop a diode, but I trust a silicon diode far more than a mechanical cutout any day.
An alternator is superior in almost every way to a dc generator.
That being said, my opinion is if you want to drive a model A the way it was built you should have a generator and run a 6 volt battery. This just happens to be what I want from a Model A. If you want a steadier output then install one of Tom's regulators, its a good product. The generator on the model A is VERY reliable, it simply has a fairly low output.
If you want cleaner power and a lot more of it you should be running a 12V alternator its a simple as that. Comparing a 7-8 volt generator which can barely burp out 20A to a 14V alternator which can produce 100-150A all day long is simply ridicules.
14v @ 100A = 1400 watts vs 7v @ 20a = 140 watts. Think its really fair or necessary to compare the two?
I ran a Delco 105A alternator on my last vehicle and often drew enough current to drop the system to 12 volts cruising down the highway. The alternator survived for many years with no problem. Sure you can pop a diode, but I trust a silicon diode far more than a mechanical cutout any day.