Alternators

2

2speed

Senior Member
I bought a 6v positive ground alternator because I felt that was easiest, and it worked great for about 600 miles. Today was HOT, and I noticed that it was ******* the ammeter. I turned on the headlights and brought it down to 20 or so amps to make it home without frying something. I believe it used to charge at like 7.2V or there abouts, now it's just making 6.88V and is according to the ammeter putting out like 15 at idle, and ******* it at anything above idle.


How reliable are these? Anyone have experience? Did I just get a bad one? Are 6 volt negative ground more reliable? Should I bite the bullet and just go to 12 Volts?


Are the starter Bendixes that fragile at 12 Volts?


When changing the coil do you opt for external resistor or internal resistor?


I'm not going back to the generator, I like having my lights not dim at stoplights and not having to worrying about cooking my battery.
 
Have you checked the battery voltage with the engine off? It is strange that the alternator is putting out 15 amps at 6.88 volts. You should not see that much current at that voltage unless there is something wrong with the battery. Is the ammeter OK? What reading do you get with the engine off and the lights on?
Bob
 
A nice gauge to have in your car is a voltmeter. I have a voltmeter and an ammeter and an alternator. I watch both meters. After I start the car the current is 15 amps, but once the voltage gets to my charged battery voltage the current drops to zero.

Bob in the post above has a valid concern. The alternator is probably OK but there is something else going on. Maybe a loose connection somewhere, the battery is starting to fail, or a current drain somewhere. You might check everything with your multimeter and take the battery to an auto parts store to have it load tested.
 
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Appears to me the alt is going into current overload which pulls down voltage, indicating a bad battery or other fault. Excessive ammeter charge reading points to a battery fault. Discharge, it lies elsewhere.

The alternator regulator should limit current as well as voltage, but it appears it does not, otherwise it would not get hot. The original 12V had this as did all the older relay regulators, but the 6V mod is a 3rd party design, and they may not have deemed the feature all that necessary, as it's an unusual occurance. Your experience is unusual, but does happen.
 
Battery cranks the car fine. I will have do some further investigating when I get home from work. I have a HF load tester and a better voltmeter than the one installed on the car.
 
Normally the Delco 10si alternator is a 3-wire 12-volt unit but years ago someone developed the 6-volt conversion. They changed the internal voltage/current control unit and added a jumper to swap polarity. These are strictly a one wire unit. One thing I've noticed about them is that output voltage is higher than what a 6-volt battery should receive. None of the ones I've checked put out 7.2-volts. It's more like 7.8 or more. Running with lights on all the time will help the battery.

There is a new voltage regulator out again that will control a stock model A generator. These set ups will at least charge the battery within normal parameters. The guy who sells them is into model T starters and has a web site.
 
Checked the battery and it tested good. Couldn't get an accurate reading on the battery voltage because two digital voltmeters jumped around, a lot. Didn't bring out the Simpson 260 yet. I order a new regulator and I'm going to try that when it comes in....
 
Be careful of your ammeter. Original replacements are hard to find. Second topic, you can have your starter rebuilt for 12 volts.

Charlie Stephens
 
I have had a Powermaster PowerGEN for ~9 years now. Never had a problem. Looks like it belongs on a Model A and isn't a modified Chevy Alternator. https://www.summitracing.com/parts/...GoeBo-LSni70fM86zpxnS3c8AvgGQwzhoCcXMQAvD_BwE

30942048998_a8a0733943_z.jpg
 
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The Bendix starter drive is prone to failure regardless of the starter's operating voltage. I suspect that heat may have effected the solid state regulator in your alternator.
 

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Conversion kits are available but that brings up another point. A person never knows who manufactured the voltage/current control units that go with these 10si conversions. If there is more than one source, then some may be better than others. Bob has the caveat for using 12-volt systems, The modern type bendix and changing the starter fields to match a 12-volt starter should make it usable but I've heard there are supply problems with the modern Bendix drive units. It seems like there is always something to put a damper on this stuff.

The modelTstarter.com voltage regulator is a cut out with a VR inside as I mentioned before. It's a bit different than John Regan's Fun Projects unit. It charges till it reaches a set voltage and then shuts the generator off. It turns on as soon as the battery voltage drops off to 6.2 volts or so. This makes the amp meter swap charge for discharge when it cuts off so it's definitely a different critter than a constant voltage regulator. They say that the internal components should always be available where the old Fun Projects VR chip was obsoleted by Texas Instruments.
 
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2speed, I still think the alternator is not the problem. There is something in the wiring or the battery that is the fault.
 
Check the charging system wiring connections from generator to the terminal box, the starter, and to the ammeter. If any are loose, it will eventually damage something.
 
Had another thought. One of the six diodes may be blown, which would be consistent with your symptoms. 3 in the diode trio and three button diodes pressed into the finned rectifier. Might check while you have it apart. Make sure replacements are for positive ground.

Your new regulator may have current protection, but don't bet on it.
 
FWIW, a few years ago I had a problem w/the alternator in a modern car. Voltage fluctuations causing the lights to flicker, turned out to be a loose connection inside the alternator.
 
The most commonly used alternator for the conversion was acclaimed to be the best alternator ever built by the local rebuilder I got parts from .
cheap to rebuild ,easy to rebuild and lasted just long enough that they wouldn’t get upset when it needed rebuilt again .
My experience is 4 rebuilds with the chevy alternator in 40 years.
The A generator had a bearing failure at 50 years since my first rebuild.
So I consider that the generator is more reliable and I run it at 14 amps.
The replacement regulators for the Delco alternator that I have taken apart have less than 1/2 the components of a original regulator.
 
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