alternator overcharge

[dingo]

perhaps ? but thats still vague....what i need is a simple flow-chart for troubleshooting, just like there is for F.Injection systems and ignition systems....i mean charging systems are a lot simpler and not rocket science. Every point in the system can be measured in volts or ohms to determine its functionality or a specific failure just like all the Bosch F.I. flow charts.

[chitwnvw]

perhaps ? but thats still vague....what i need is a simple flow-chart for troubleshooting, just like there is for F.Injection systems and ignition systems....i mean charging systems are a lot simpler and not rocket science. Every point in the system can be measured in volts or ohms to determine its functionality or a specific failure just like all the Bosch F.I. flow charts.

Except you might have an unintended ground somewhere...

[Hippie]

perhaps ? but thats still vague....what i need is a simple flow-chart for troubleshooting, just like there is for F.Injection systems and ignition systems....i mean charging systems are a lot simpler and not rocket science. Every point in the system can be measured in volts or ohms to determine its functionality or a specific failure just like all the Bosch F.I. flow charts.

I made my living for most of the last 25 years troubleshooting mechanical, electrical, and electronic control systems and machinery. I can tell you a few things about T-shooting:

1. Flow charts are highly over rated. They do not translate well into zeroing in on the actual failure...which can be a chafed wire that grounds out only at certain temperatures, as most failures are intermittent, and you are lucky yours is not.

2. It is impossible to tell you what is wrong with any certainty over the internet and without a schematic in hand.

3. The only thing you can do is study how it operates and why, don't overthink the fix, narrow it to the component (eg alternator or regulator or wiring) by eliminating all other possibilities by forcing conditions that should make the component function, and replacing the non-responsive part.

4. Accept that you will often never know what little blob of solder let go deep inside the component. Just fix it.

[dingo]

i respectfully disagree. Flow charts, if well designed..can be very helpful and time-saving, and in simple electrical systems such as these, it should not be hard to trace an issue down to a single failed component, or compromised insulation or contact.

perhaps if you are on the clock or in a business, its more profitable to simply replace units...but neither applies to myself

[dingo]

http://www.pelicanparts.com/914/parts/E ... ic_74E.jpg

click to enlarge....

The voltage regulator "watches" the voltage at the D+ point, which should be the same as that applied to the battery. It now changes the short between the D+ and DF terminals into a variable resistance. This effectively controls the field current (whose source is now the output from the D+ terminal, and not the charge warning lamp) and thus regulates the output voltage of the alternator.

my question: How does D+ access the batt. status ? B+ is strictly 'outgoing', hemmed in by diodes... so it cant be via B+......????

[Hippie]

...its more profitable to simply replace units...

No, it's not.
I meant that it is important to fix it but not important to analyze the system more than you have to to affect the repair.

Been here? Maybe this will help:

http://www.ratwell.com/technical/ChargingSystem.html

[dingo]

thanks...i just discovered the ratwell diagrams this afternoon..just what i was looking for !


beyond merely solving the problem or replacing a unit, i have an unquenchable need to understand the systems..its not always the fastest route, but it is ultimately more satisfying (for me)

[Amskeptic]

thanks...i just discovered the ratwell diagrams this afternoon..just what i was looking for !


beyond merely solving the problem or replacing a unit, i have an unquenchable need to understand the systems..its not always the fastest route, but it is ultimately more satisfying (for me)

I'm with you. Now, when you have the chance, spell out what your inner mental question was and what and how you found the answer. I have been pretzeling my brain around AFM ECU mapping, with only observable effects to guide me. Really overwhelms my mental processor to realize that there is no linearity and that the map is a fricken moonscape are variables.
Colin

[dingo]

Im just plodding along, one step at a time, but I AM making progress in understanding the system...to the point where i can describe the charging system in one long,rambling sentence !

-dash light shows normal behavior. Battery is New. Multimeter double checked with another for correct readings.

D+ to DF: 24 Ohms (harness disconnected)

- Ign OFF: D+ = 0 V , DF= 0 V

Ign ON: D+ = 1.6 V , DF =0 V

Engine ON: D+ = 15.7 V , DF =9.3V

so Im not sure what the standard readings should be...

..but either the incoming D+ is abnormally high and the reg is just doing its job
OR Reg(s) is malfunctioning and not translating [incoming D+ to outgoing DF] correctly
OR ?

[Hippie]

I think around 5 volts on the DF.

The key is, and you probably know this, but the DF is the field coil. On an alternator, or generator the more current to the field coil, the stronger its magnetic flux. The strionger the flux, the higher voltage/power the Stator, (or rotor in a generator) puts out.
The stator or rotor is the main coil and is the output to the battery and electrical system. The field coil is just the control, the voltage reg "turns up" the voltage to the field coil when the battery needs more charge. The electrical system draws more current or the battery goes down in charge, the system voltage goes down a little, the reg senses this and turns up the time that the field coil is pulsed, which makes its average voltage and current go up, the magnetic field it puts out gets stronger, and the output of the gen/alt voltage goes up to keep up.

[dingo]

I think around 5 volts on the DF.

The key is, and you probably know this, but the DF is the field coil. On an alternator, or generator the more current to the field coil, the stronger its magnetic flux. The strionger the flux, the higher voltage/power the Stator, (or rotor in a generator) puts out.
The stator or rotor is the main coil and is the output to the battery and electrical system. The field coil is just the control, the voltage reg "turns up" the voltage to the field coil when the battery needs more charge. The electrical system draws more current or the battery goes down in charge, the system voltage goes down a little, the reg senses this and turns up the time that the field coil is pulsed, which makes its average voltage and current go up, the magnetic field it puts out gets stronger, and the output of the gen/alt voltage goes up to keep up.

Thx..that does make perfect sense. So, in theory, if the reg sees 15.7V at the D+, it should be bringing the DF way down.

also i was wondering down the reg varied the output...varied pulse times...got it !

[dingo]

well, according to the gentleman at Bosch/Australia (dont ask!)...rotor resistance should be 3 Ohms. I disconnected the reg and checked DF to ground and got 11.2 Ohms...dont know whether thats way out or still acceptable

This is a very old system which is no longer manudfactured since 1995.

It uses an external regulator.Check the warning lamp is on at ignition on engine not running.
Run the engine, with a volt meter measure the voltage on D+ terminasl it should be 14.2 Volts. The warning lamp should go out.
There are many possible causes that the alternator will not charge. Test the rotor resistance it should be approx 3 ohms.
Inspect the brushes for wear. Could be a regulator fault. Inspect the regulator points for burning.

The regulator is difficult to adjust unless you have the right equipment and tools.

Hope this helps

Robert Bosch(Australia) Pty Ltd
Robert G Tait
Supervisor
Service Engineering Group
Ph.+6139541559
Fax +61395434293

Email. bob.tait@au.bosch.com

[Hippie]

Sounds way out to me. Almost 400% out.

Yeah the electronic regs...some anyway, use a transistor like a variable resistor to change voltage to the field (again, the output control) coil. The traditional mechanical ones have a relay that opens and closes real fast...like 300-400 times a second. Vibration really. The lower the voltage the Alt/Gen is putting out on B+ (D+ in German) the more percent of the cycle the contact is closed in that vibration...until it is closed all the time and never opens if the voltage keeps falling. That excites the field coil more and more to a stronger magnetic field to raise D+ output as the relative rotating cuts through the stronger field. When out put is high, the contacts can also be always open causing the field coil to idle along with only its residual magnetism and cut output so the various lightbulbs dont burn out or the battery boil over.

So as the engine turns faster, the output should be cut down to keep it relatively even. Otherwise, you'd get really higher voltage at high RPMs and low electrical load.
I read that a modern alternator without the battery connected to help stabilize the voltage along with the regulator, can put out more than 200 volts as the engine is rev'ed.

[Amskeptic]

Sounds way out to me. Almost 400% out.

Yeah the electronic regs...some anyway, use a transistor like a variable resistor to change voltage to the field (again, the output control) coil. The traditional mechanical ones have a relay that opens and closes real fast...like 300-400 times a second. Vibration really. The lower the voltage the Alt/Gen is putting out on B+ (D+ in German) the more percent of the cycle the contact is closed in that vibration...until it is closed all the time and never opens if the voltage keeps falling. That excites the field coil more and more to a stronger magnetic field to raise D+ output as the relative rotating cuts through the stronger field. When out put is high, the contacts can also be always open causing the field coil to idle along with only its residual magnetism and cut output so the various lightbulbs dont burn out or the battery boil over.

So as the engine turns faster, the output should be cut down to keep it relatively even. Otherwise, you'd get really higher voltage at high RPMs and low electrical load.
I read that a modern alternator without the battery connected to help stabilize the voltage along with the regulator, can put out more than 200 volts as the engine is rev'ed.

So let's review dingo's complaint:
rotor resistance should be 3 Ohms. I disconnected the reg and checked DF to ground and got 11.2 Ohms.

How would high resistance in the field circuit yield an overcharge? Would it fool the regulator into thinking that the field voltage/magnetism is artificially low, thus cranking up the alternator output?
Colin

[dingo]

my dad's comment on the resistance measurement of 11ohms :

Basically, the average resistance of the rotor windings, across the slip-rings is in the range of 3 ohms. DF is connected to the floating side slip ring and the other slip ring goes to earth.

The 8 extra ohms could be due to bad brush contact with the slip rings or worn slip rings where the brush aren't making proper contact.


Can you check the resistance between the 2 slip rings directly with harness disconnected.and bypassing the DF terminal ??