Alternator Question
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From: Wal-Mart, Women's section.
Alternator Question
Can a diode in an alternator be replaced or does the whole unit need replaced?
I've replaced alternator's before but if I can replace a small piece and save spending $200 on a new alternator, I'd rather much more do that....
Thanks guys...
I've replaced alternator's before but if I can replace a small piece and save spending $200 on a new alternator, I'd rather much more do that....
Thanks guys...
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From: Wal-Mart, Women's section.
The Alternator
The alternator uses the principle of electromagnetism to produce current. The way this works is simple. If you take a strong magnet and pass it across a wire, that wire will generate a small voltage. Take that same wire and loop it many times, than if you pass the same magnet across the bundle of loops, you create a more sizable voltage in that wire.
There are two main components that make up an alternator. They are the rotor and the stator. The rotor is connected directly to the alternator pulley. The drive belt spins the pulley, which in turn spins the rotor. The stator is mounted to the body of the alternator and remains stationary. There is just enough room in the center of the stator for the rotor to fit and be able to spin without making any contact.
The stator contains 3 sets of wires that have many loops each and are evenly distributed to form a three phase system. On some systems, the wires are connected to each other at one end and are connected to a rectifier assembly on the other end. On other systems, the wires are connected to each other end to end, and at each of the three connection points, there is also a connection to the rectifier. More on what a rectifier is later.
The rotor contains the powerful magnet that passes close to the many wire loops that make up the stator. The magnets in the rotor are actually electro magnets, not a permanent magnets. This is done so that we can control how much voltage the alternator produces by regulating the amount of current that creates the magnetic field in the rotor. In this way, we can control the output of the alternator to suit our needs, and protect the circuits in the automobile from excessive voltage.
Now we know that every magnet has a north and a south pole and electro magnets are no exception. Our rotor has two interlocking sections of electro magnets that are arranged so that there are fingers of alternating north and south poles. that are evenly distributed on the outside of the rotor.When we spin the rotor inside the stator and apply current to the rotor through a pair of brushes that make constant contact with two slip rings on the rotor shaft. This causes the rotor to become magnetized. The alternating north and south pole magnets spin past the three sets of wire loops in the stator and produce a constantly reversing voltage in the three wires. In other words, we are producing alternating current in the stator.
From what I found online, doesn't look like they can just be replaced? Anybody attempted this?
The alternator uses the principle of electromagnetism to produce current. The way this works is simple. If you take a strong magnet and pass it across a wire, that wire will generate a small voltage. Take that same wire and loop it many times, than if you pass the same magnet across the bundle of loops, you create a more sizable voltage in that wire.There are two main components that make up an alternator. They are the rotor and the stator. The rotor is connected directly to the alternator pulley. The drive belt spins the pulley, which in turn spins the rotor. The stator is mounted to the body of the alternator and remains stationary. There is just enough room in the center of the stator for the rotor to fit and be able to spin without making any contact.
The stator contains 3 sets of wires that have many loops each and are evenly distributed to form a three phase system. On some systems, the wires are connected to each other at one end and are connected to a rectifier assembly on the other end. On other systems, the wires are connected to each other end to end, and at each of the three connection points, there is also a connection to the rectifier. More on what a rectifier is later.
The rotor contains the powerful magnet that passes close to the many wire loops that make up the stator. The magnets in the rotor are actually electro magnets, not a permanent magnets. This is done so that we can control how much voltage the alternator produces by regulating the amount of current that creates the magnetic field in the rotor. In this way, we can control the output of the alternator to suit our needs, and protect the circuits in the automobile from excessive voltage. Now we know that every magnet has a north and a south pole and electro magnets are no exception. Our rotor has two interlocking sections of electro magnets that are arranged so that there are fingers of alternating north and south poles. that are evenly distributed on the outside of the rotor.
Now, we have to convert this alternating current to direct current current. This is done by using a series of 6 diodes that are mounted in a rectifier assembly. A diode allows current to flow only in one direction. If voltage tries to flow in the other direction, it is blocked. The six diodes are arranged so that all the voltage coming from the alternator is aligned in one direction thereby converting AC current into DC current.
There are 2 diodes for each of the three sets of windings in the stator. The two diodes are facing in opposite directions, one with its north pole facing the windings and the other with its south pole facing the windings. This arrangement causes the AC current coming out of the windings to be converted to DC current before it leaves the alternator through the B terminal. Connected to the B terminal of the alternator is a fairly heavy wire that runs straight to the battery.
Current to generate the magnetic field in the rotor comes from the ignition switch and passes through the voltage regulator. Since the rotor is spinning, we need a way to connect this current from the regulator to the spinning rotor. This is accomplished by wires connected to two spring loaded brushes that rub against two slip rings on the rotor's shaft. The voltage regulator monitors the voltage coming out of the alternator and, when it reaches a threshold of about 14.5 volts, the regulator reduces the current in the rotor to weaken the magnetic field. When the voltage drops below this threshold, the current to the rotor is increased.
There is another circuit in the alternator to control the charging system warning lamp that is on the dash. Part of that circuit is another set of diodes mounted inside the alternator called the diode trio. The diode trio takes current coming from the three stator windings and passes a small amount through three diodes so that only the positive voltage comes through. After the diodes, the wires are joined into one wire and sent out of the alternator at the L connection. It then goes to one side of the dash warning lamp that is used to tell you when there is a problem with the charging system. The other side of the lamp is connected to the run side of the ignition switch. If both sides of the warning lamp have equal positive voltage, the lamp will not light. Remove voltage from one side and the lamp comes on to let you know there is a problem.
This system is not very efficient. There are many types of malfunctions of the charging system that it cannot detect, so just because the lamp is not lit does not mean everything is ok. A volt meter is probably the best method of determining whether the charging system is working properly
There are 2 diodes for each of the three sets of windings in the stator. The two diodes are facing in opposite directions, one with its north pole facing the windings and the other with its south pole facing the windings. This arrangement causes the AC current coming out of the windings to be converted to DC current before it leaves the alternator through the B terminal. Connected to the B terminal of the alternator is a fairly heavy wire that runs straight to the battery.Current to generate the magnetic field in the rotor comes from the ignition switch and passes through the voltage regulator. Since the rotor is spinning, we need a way to connect this current from the regulator to the spinning rotor. This is accomplished by wires connected to two spring loaded brushes that rub against two slip rings on the rotor's shaft. The voltage regulator monitors the voltage coming out of the alternator and, when it reaches a threshold of about 14.5 volts, the regulator reduces the current in the rotor to weaken the magnetic field. When the voltage drops below this threshold, the current to the rotor is increased.
There is another circuit in the alternator to control the charging system warning lamp that is on the dash. Part of that circuit is another set of diodes mounted inside the alternator called the diode trio. The diode trio takes current coming from the three stator windings and passes a small amount through three diodes so that only the positive voltage comes through. After the diodes, the wires are joined into one wire and sent out of the alternator at the L connection. It then goes to one side of the dash warning lamp that is used to tell you when there is a problem with the charging system. The other side of the lamp is connected to the run side of the ignition switch. If both sides of the warning lamp have equal positive voltage, the lamp will not light. Remove voltage from one side and the lamp comes on to let you know there is a problem.
This system is not very efficient. There are many types of malfunctions of the charging system that it cannot detect, so just because the lamp is not lit does not mean everything is ok. A volt meter is probably the best method of determining whether the charging system is working properly
From what I found online, doesn't look like they can just be replaced? Anybody attempted this?
I Voted For Bill and Opus
Joined: Nov 2007
Posts: 2,040
Likes: 9
From: Cheyenne, Wyoming
You normally replace the entire diode board, be sure to replace the bearings, and the brushes. Check the stator and field coil for shorts, look at the slip rings if any of these parts are in bad shape then replacement for the whole unit is in in order. I have done this in past years was pleased with the results, and the money I saved, but it seems like everytime I did it the Car Gods would take revenge on me and something else in the alternator would fail causing me replace the entire unit anyway.
P.S. I usually replaced the internal voltage regulator as well.
P.S. I usually replaced the internal voltage regulator as well.
Last edited by transmaster; Oct 13, 2009 at 02:38 PM.
Huh?
Joined: May 2009
Posts: 3,685
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From: Stockbridge Ga
Yes you can replace the diodes.. but.. unless your good with a soldering iron i wouldnt attempt it.. the heat from the soldering iron alone can mess the diodes up.. thats what was wrong with my alternator... i decided to just replace the whole thing with a used one..
Of course me being half retarded i did mine all crazy and used a alternator that didnt even go to the truck lol.. but im kinda glad i did.. it was a good experience and i learned alot about alternators lol.. thats why i love working on my truck...
Of course me being half retarded i did mine all crazy and used a alternator that didnt even go to the truck lol.. but im kinda glad i did.. it was a good experience and i learned alot about alternators lol.. thats why i love working on my truck...
I Voted For Bill and Opus
Joined: Nov 2007
Posts: 2,040
Likes: 9
From: Cheyenne, Wyoming
Yes you can replace the diodes.. but.. unless your good with a soldering iron i wouldnt attempt it.. the heat from the soldering iron alone can mess the diodes up.. thats what was wrong with my alternator... i decided to just replace the whole thing with a used one..
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I NOM NOM NOM Threads...
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From: Wal-Mart, Women's section.
All right that's the info I was looking for. I'm not shabby with a soldering iron but nor am I really good.
I'll just get a rebuilt unit and call it a day. Thanks for the help guys...
I'll just get a rebuilt unit and call it a day. Thanks for the help guys...
