Alternator Question

[john charlton]

The alternator my CCPU suddenly decided to charge off the clock and in very short order fried the ampmeter . Had another one a swap meet $ 10 special so fitted it ever hopeful but dead as a dodo nuddinks . Put a regular generator on and back in business . I saw Paul Shinns alternator video today and thought maybe I could make a good one out of two . Sadly they are similar inside but not the same . Luckily the Delco Remy one is identical to the video this is the zero charge one . The stator and bearings look good and the windings look good too no smell of burnings . I can most likely buy parts here I have a part number on the tri rectifier and also Pauls video gives the regulator number . What think ye learned gentlemen of The Barn ??? These are the first units I have taken apart .

John in very hot record breaking Suffolk County England .

[katy]

First thing l would to is test all the diodes.

[Patrick L.]

Generally just the regulator fails causing no charge condition.

Having one full field itself is pretty rare. So just check everything carefully and I'd recommend changing the diode bridge. Haven't bought any of these parts lately, but, they weren't expensive.

[rotorwrench]

Kits are available here on flea-pay and from other sources. They come with the controller module and the diode bridge as well as bearings and such. A person can convert a 12 to 6-volt or go back to 12-volt if they want. I'm not sure about availability in the UK though.

A good 3-brush gen is hard to beat but the alternators are less expensive. I don't like the high voltage output on the conversions and can't speak for the quality of the parts either. I've had an alternator fail before and it did the same thing. I use them on the old Ford tractor but it runs 12-volts.

[Badpuppy]

An alternator requires residual magnetism to spin up, just like a generator. If it has sat for months it may need to be "polarized" again to restore the magnetic field. An alternator regulator needs a positive voltage applied to pin 1 of the connector, regardless of output polarity. For a positive ground unit, simply touch pin 1 (nearer output post) to the case with a screwdriver.

This could explain your non-starting problems.

[Kenjt]

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So, which is better a generator or an alternator? I always thought all Model A's were built with a generator. So, why even switch to an alternator?

[ndnchf]

Originally Posted by Kenjt

So, which is better a generator or an alternator? I always thought all Model A's were built with a generator. So, why even switch to an alternator?

No doubt an alternator is better - technology moves forward. The real question is - is an alternator necessary? A rebuilt stock generator is perfectly good for most uses. Especially with the latest LED headlight options. With these, there is no need for the high current output of an alternator, or for that matter - even high output of a generator. A stock generator with the 3rd brush at its lowest output setting can provide enough current to run with LED headlights on and still maintain a slight positive charge on the ammeter. This greatly reduces heat and wear of the generator. As such, it will last a long time.

[nkaminar]

My experience with alternators is that brushes go bad, like in a generator. However that was years ago for my 1971 Datsun. The dealer wanted to sell me a new alternator, which made me mad. I bought the brushes for $2.89 and installed them myself.

[Kenjt]

nkaminar thanks for your reply. As you may have noticed, I've been having a lot of problems keeping my battery charged. I discovered that my car has an alternator and have wondered if this could be part of my problem. I don't know how old it is or if it is causing my problem. I've come to the conclusion that a new generator might solve the problem.

[jrelliott]

Kenjt, if you are using a single wire alternator, then there is a small drain on the battery while the car is off due to current being applied to the field. There is a connection between the charging wire out of the alternator to pin 1 . Remove the fuse if you have one when you shut off the car or if you have a disconnect switch turn it off.

[Kenjt]

Originally Posted by jrelliott

Kenjt, if you are using a single wire alternator, then there is a small drain on the battery while the car is off due to current being applied to the field. There is a connection between the charging wire out of the alternator to pin 1 . Remove the fuse if you have one when you shut off the car or if you have a disconnect switch turn it off.

Thanks for the tip. I wonder if, now that I know my charger is working, if I just keep it plugged in it will overcome the potential issue you mention. I haven't yet checked the type of alternator in the car and if it is a single wire.

[MrBruce]

I switched because we do a lot of night driving and it's a pain to keep moving the brushes for a higher charge rate than you need for daytime driving, and then when driving during the daylight hours your charge rate is to high. I have run alternators for over 45 years and never a bit of trouble. You can pull one blolt and put the generator back if your showing your Model A (which not many people go back after running a alternator) I don't think. Just my experience

[rotorwrench]

The 10si alternator has been the mainstay for most single wire conversions for may years but they are not infallible. A lot of electrical system problems are due to loose or poor electrical connections. A person has to careful about the way their wiring is run on these old cars. Ford didn't put any extra insulation on their wiring and they would only use metal clips to hold the wires in key locations. Shorts can happen under the dash panel when the wires rub things with no extra insulation. Modern ignition switches and panel lights are likely the biggest cause of shorts. There isn't much room in there.

An alternator can do some damage if a wire shorts out somewhere and there is no main fuse for wire protection. Even the 6-volt conversion alternators put out a lot more amps than the 3-brush OEM generator. If a short happens, it can burn the amp meter and the alternator as well as the wire that shorts out.

Alternators like the modified 6-volt GM 10si have the electronic voltage & current controller inside along with the diode bridge and the polarity jumper (6-volt positive ground only). Any of this stuff can be damaged when shorted out or when using jumper cables too long. An alternator should show it's output voltage at the battery when running. Most of them put out too much voltage at around 7.5 to 7.8 volts. I would prefer that they only put out 7.0 to 7.2 volts but I can't change the design.

A three brush generator has it's voltage controlled by the battery. They are good for a steady 15-amps or a short term output of 20-amps max. This all depend on how the 3rd brush is adjusted so it can be low without lights but has to be adjusted up to run lights. They tend to overcharge too but that's just the nature of the beast. Care has to be taken to insure the battery is well connected at all times. If it has a weak or bad connection then the generator can experience excessive output and burn itself up.

[nkaminar]

Kenjt, I highly recommend adding a volt meter to your car. It can be added anywhere but there are brackets available for under the instrument panel. The volt meter will tell you the condition of the battery when you first turn on the ignition and the condition of the battery when it is being charged while driving the car. Mine indicates 14 volts after a few miles (12 volt system).