Why does this wire Spark?

[jchochole]

I just got a '28 Sedan and this yellow wire will spark when it touches the alternator post. The car came like this- can anyone help? The car was converted to 12V by previous owner and this little wire shows 12v on a voltmeter. Must be a direct connection to the battery, but why?

Thanks,
Jim

[Bob C]

That wire goes to the ammeter and then to the starter and battery.

Bob

[jchochole]

So, now that I have an alternator on the car, it doesn't seem like it is needed. Like said, it reads 12V on it with a tester.

[Bob C]

I don't see how you are going to keep the battery charged with out that wire hooked up.

[cpf240]

Originally Posted by jchochole

So, now that I have an alternator on the car, it doesn't seem like it is needed. Like said, it reads 12V on it with a tester.

Then how is the alternator supposed to charge the battery?

Those other two wires go to the horn and the light switch...

[JDupuis]

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That wire is used to recharge the battery......show the charge rate. Jeff

[cpf240]

To get back to the original question, has the alternator been taken in and tested? Perhaps the diode trio has failed, and it is shorted.

[Y-Blockhead]

OK, we established that is the charge wire. You didn't mention when it sparked. Does it spark when the engine is not running? (Alternator not turning?).

You shouldn't have a draw on the battery when it is just sitting there. It sounds like you may have a bad diode in the alternator.

[Purdy Swoft]

The wire that connects to the alternator or the cut out if you ran a generator is suppose to be hot . if the battery is 12 volt it will show 12 volt . The alternators that are sold for use on the model A will have a built in voltage regulator that prevents current entering the alternator . when the engine runs and reaches a certain RPM the regulator will allow the alternator to charge back through the hot wire to the ammeter and back to the battery . If a generator is used the cut out will serve the same purpose but won't give voltage regulation. If the ammeter shows a discharge when the engine isn't yrunning there will either be a problem with the alternator or a dead short somewhere in the system . If a generator is osed it will usually indicate stuck points in the cut out .

[Purdy Swoft]

The yellow wire with black tracer is live . If the yellow wire with black tracer isn't connected to the alternator it will spark any time that it is touched to anything that it can ground on including the post on the alternator . It may be hard to understand how the alternator can charge back through a live wire . Thats just the waty that it works .

[jchochole]

Thanks for the help- to answer the good question, I touched the yellow wire to the alternator post and got the spark when the car was off and cold. I didn't want to fry it in case that was an incorrect connection- but it sounds like connecting it is okay?

I am attaching a couple more pics, the alternator is stamped "12VoltNeg" and none of my lighting is connected for some odd reason (guy cut all the wires) so will my wiring handle the 12V system? Haven't checked bulbs yet.

Thanks for the support, guys! I am attaching a pic of my terminal box and horn wire too, since that gets attached to the alternator post, right- So two wires to the alternator then? Even if it sparks?

**I tested the alternator (car not running) with a voltmeter and shows "zero" touching the post and a ground. So, I assume the diode is good then.

Jim

[Purdy Swoft]

It looks like a mess has been made out of the wiring. the best thing that you could do is replacr the wiring harnesses because of what all has been screwed up . there should be a hot yellow wire with black tracer that connects to the alternator. the headlamp and horn wiring would also connect to the alternator . Because I don't know what all else has been screwed up, I don't want to say anything that could cause other problems.

[Tom Wesenberg]

How big is the spark?
Leave the wire off until the problem is fixed, or you'll kill the battery, or even start a fire.

Your lower coolant pipe is the 1930-1 style, rather than the correct 1928-9 one.

[jchochole]

Purdy- yes, there is indeed a hot yellow wire (that's the sparker) that goes to the alternator. Looking at schematics with colors, the wiring looks in order in the terminal. So, just not sure why I am getting a good spark at the alternator post.

[midgetracer]

If you are getting a spark at the alternator post when the engine is not running there is a problem in the alternator.

[pooch]

Is the battery hooked up correctly?

If the alternator is negative earth and the battery is hooked positive earth, I am sure that will cause a spark.

It blows the main fuse on modern cars if you hook up wrong.

[jrelliott]

If it is a single wire alternator, there is a small draw from the battery while the vehicle is turned off. This is the field windings of the alternator. There is very little residual magnetism like in a generator which will induce a voltage when the generator is spun. You need a magnetic field to have the wires cross to induce a voltage. This is the main reason you cannot push start a vehicle with an alternator but can with a generator.

[Will N]

Originally Posted by jchochole

Thanks for the help- to answer the good question, I touched the yellow wire to the alternator post and got the spark when the car was off and cold. I didn't want to fry it in case that was an incorrect connection- but it sounds like connecting it is okay? ...



**I tested the alternator (car not running) with a voltmeter and shows "zero" touching the post and a ground. So, I assume the diode is good then.

Jim

What setting did you have your voltmeter on? You should have it on Continuity. With the wire disconnected, car not running, from the post to ground you should have no continuity.

As others have said, that yellow wire is supposed to be hot. If it's sparking when touching the post, that tells me the post is grounded. It should not be when the alternator isn't spinning and is not putting out current. The diode is an/off switch. It disconnects the circuitry in the alternator until the alternator starts putting out current. I feel that your diode is shot.

[jchochole]

Okay, sounds like I need to take my alternator to a shop to be tested. Thanks, guys!

I checked for continuity and nothing, no noise out of my meter when I went from post to ground.

[jchochole]

I just checked and my battery is hooked up Negative ground, and my alternator is also negative ground.

I've never had an A with a Negative ground, why do guys switch that?

[Purdy Swoft]

Because the alternators that are offered for 12 volt use on the model A are all negative ground. I run my roadster 12 volt positive ground with the original unmodified generator and no changes to the original wiring is necessary.

[Y-Blockhead]

Originally Posted by Purdy Swoft

Because the alternators that are offered for 12 volt use on the model A are all negative ground. I run my roadster 12 volt positive ground with the original unmodified generator and no changes to the original wiring is necessary.

What Purdy Said...

Purdy, with your set up do you need to run a regulator of some sort, such as the one from Fun projects http://www.funprojects.com/products/10505r.aspx

I run a Powermaster PowerGEN, mainly because I hate the look of a alternator on A Model A engine. If it ever goes out, I may put the generator back on with a Fun Projects regulator.

[Keith True]

I've only seen one person so far that that has posted the fact that there is a parasitic drain with the one wire converted alternators.It is tiny,I have one on a wood chipper that will still start in the spring after sitting all winter.I have one on my big air compressor that seems to sit a year before it is drained off.My loader has one that drains in about two months,but that one has a big spark when the wire is pulled off.I know the alternator has a problem,but it does charge and I just use the cutoff switch.If your alternator drains the battery in a couple of weeks,or makes a big spark,then there is something wrong.That parasitic drain won't register on an ammeter.

[Purdy Swoft]

Originally Posted by Y-Blockhead

What Purdy Said...

Purdy, with your set up do you need to run a regulator of some sort, such as the one from Fun projects http://www.funprojects.com/products/10505r.aspx


I run a Powermaster PowerGEN, mainly because I hate the look of a alternator on A Model A engine. If it ever goes out, I may put the generator back on with a Fun Projects regulator.



I do use the Fun Projects can style voltage
regulator. It will still work with just a good cut out but will have no voltage regulation. I would reccomend the Fun Projects regulator on any model A generator. It looks like a cutout and is just as easy to install . The Fun Projects voltage regulator is offered in six , eight and twelve volt versions and can be had in positive or negative ground. For the six volt version you need to adjust the third adjustable brush for a 15 amp maximum charge rate , The twelve volt version is set for a maximum rate of 8 amps . John Regan , the makertold me that I could set mine for a maximum rate of 10 amps if I felt that I needed it for brighter lights. I use the 35 watt halogen bulbs that fit the original sockets and they are plenty bright plus two tail lamps. I run mine pretty much like original . If a person wants to run a lot of high amp draw accessories , this may not be the best choice . One of the things that I really like about this set up is that the generator doesn 't have to be dissassembled to install it .The other voltage regulators that are on the market still require the use of the sometimes troublesome cut out . The Fun Projects regulators have no points to stick like the original cutouts do . The Nurex internal voltage regulators that take the place of the third brush are not available in 12 volt I have had years of trouble free service from the six and twelve volt versions of the Fun Projects voltage regulators ...

For some reason I'm having problems getting this message to post ...

Try this, Maybe it will post

[Purdy Swoft]

Originally Posted by jchochole

Purdy- yes, there is indeed a hot yellow wire (that's the sparker) that goes to the alternator. Looking at schematics with colors, the wiring looks in order in the terminal. So, just not sure why I am getting a good spark at the alternator post.

Read Keith Trues post # 23 Keith knows his stuff . The one wire alternators can and usually do have a small parasitic draw . Its not usually enough to cause a problem if the car is used on a somewhat regular basis but could cause a spark at the terminal when the yellow wire with black tracer is connected .I'm not making any suggestions only because if there are other problems I don't want to cause more . Good luck and it will probably be OK .

[jchochole]

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I am leaning towards buying a 6V Positive Ground alternator, and going back to a 6V positive grounded battery, that way I can use all the existing bulbs and stock ammeter in the car.

I don't need a 12Volt system. It looks like if I remove the ballast resistor and drop a 6V battery back in for positive ground, I am back to stock.

Does anyone thing I am missing anything?

[jchochole]

Okay here's the answer, I ran the 12V alternator to get it bench tested and it is stone cold dead. Wouldn't even accept voltage into it. That's why it sparked.

[Purdy Swoft]

I would get an original generator and a Fun Projects voltage regulator . Then you would have voltage regulation . You could choose the voltage by which voltage regulator that you chose . You would still have the original look even if you chose to keep and use your 12 volt battery . I use the original type 20 amp ammeter with my 12 volt setup . If you are running a 30 amp ammeter it would still work . The ammeter only registers amps , not volts. You would need to remove the ballast resistor and use a 3.0 OHM coil. the coil would cost less than buying a new six volt battery even if you used a pertronix flame thrower coil like I use on mine . I chose to convert to 12 volts for a more powerful and reliable electrical system . Twelve volt batteries and components are readily available almost anywhere and usually less expensive . Twelve volts cranks quickly . Light bulbs are cheap , especially if you use the original style bulbs like all the vendors sell for 12 volt use . I chose the 35 watt halogen bulbs that fit the original sockets . My lights are brighter than original . It may sound complicated but it really isn't . Just a thought .

[Bikerider58]

I have not had my A long, and now have a 6v alternator, LED tail lights, 12v power supply for gadgets and LED driving lights. If I would have thought about it more before buying the 6v LED tail lights, I probably would have just gone to 12v with regulator for all the reasons Purdy states.

The wiring is good except for lack of fusing. I added a main fuse and fuse block splitting the circuits. Stuffing the runs into asphalt cloth loom is a pain, but needed to look right.

Make it your own and have fun with it.

[Y-Blockhead]

Originally Posted by Bikerider58

I have not had my A long, and now have a 6v alternator, LED tail lights, 12v power supply for gadgets and LED driving lights. If I would have thought about it more before buying the 6v LED tail lights, I probably would have just gone to 12v with regulator for all the reasons Purdy states.

The wiring is good except for lack of fusing. I added a main fuse and fuse block splitting the circuits. Stuffing the runs into asphalt cloth loom is a pain, but needed to look right.

For my added "accessories" (Turn signals, Fog Lights, Temperature Gauge, etc. I use ClassicBraid by Painless Wiring. It is a split loom that looks (somewhat) vintage compared to others (like corrugated plastic) as seen in the picture in post #22 covering the water temperature gauge line.

[Glenn Thoreson]

That wire should go to the ammeter. If you are using a one wire alternator you need to forget this wire and make sure the alternator wire(s) go directly to the battery in whatever fashion you prefer. You may need to re-route the feed to the ignition switch. Don't run an alternator through the stock ammeter. It's not meant to handle the amperage and will burn out or start a fire. They were bad enough with a 20 Amp 6 volt generator.