16 + volts

some of you may remember me posting about how my warning lights were dimming in and out along w/ my head lights a while back.

well, I looking into the matter a bit more today. it turns out when the rpms go up the voltage goes up...a lot!

Off it runs 12.1 (what it should)
Idle it runs 13.2 (what it should)

Anywhere above 2 grand it goes way up, I saw it go up to 16.4!! After that I just shut it off.

While driving everything pulses in and out to the RPMs. Faster the RPM, faster the pulse. Last night my friend thought I was flashing him because of the voltage difference.

any help would be very apriciated!!!!!!!!!!!!!!!!!!!!!!!!!!!!!1

Sounds like the voltage regulator in the alternator is shot, plus it's sending out dirty current. Get thee a replacement or rebuild before you ruin the battery or something electronic with the overvoltage. Drive slowly.

yeah, that was what I was thinking...I have to go get a new alternator. The shop that installed mine before I got the car (1 week) wont honor the warantee, and is trying to tell me that it's compleatly fine, and is something else in the wiring of the car *coughbscough*

[lee]

1: Alldata says the Alternator should put out 14.2 - 14.8 Volts - I'm assuming that's at idle (or maybe 1500 rpm?).

2: Is 13.2 is correct at idle - isn't that about what the battery should show with engine off?

3: I always thought the voltage regulator's purpose to prevent overcharging, not regulating the volts themselves, not true?

4: I think I understand generators, and always assumed alternators were somehow the same excepting the need to rectify the current. I thought increasing the engine speed would produce more current, but not much voltage change - thinking somehow this was a basic physical property.

5: Anybody brave enough to take me through alternator 101, please PM me.

[oab_au]

Originally posted by EverclearAtMSU
yeah, that was what I was thinking...I have to go get a new alternator. The shop that installed mine before I got the car (1 week) wont honor the warantee, and is trying to tell me that it's compleatly fine, and is something else in the wiring of the car *coughbscough*

Alternator may be ok, Could be a resistance between the alt and the battery. This would mean that the reg sees less battery voltage than there is, so it keeps going up till it sees 14.7v. If you see 16.4 volts, then there is a 2volt resistance between the alt and battery.
The Auto electrician should be able to find it.
Harvey.
P.S. may .be due for the alt wiring update.

Hmm.. this is from the manual.

When any of the following problems occur, the charge light
illuminates.
* No voltage generation: Brush wear exceeds specified limits,
field coil circuit is broken, etc.
* Excessive output: Output voltage is greater than about 16
volts.
* Terminal ‘‘B’’ disconnection: Harness is disconnected from
generator terminal ‘‘B’’.
* Terminal ‘‘S’’ disconnection: Harness is disconnected from
generator terminal ‘‘S’’. In this case, voltage is slightly
greater than specified regulated voltage; however, voltage
regulation is still controlled and the battery is prevented
from being overcharged.

ON-VEHICLE TESTING
Turn ignition on, with engine off. If charge light does not
illuminate, disconnect generator body harness connector. If charge light does not illuminate when terminal ‘‘L’’ of harness connector is grounded, replace charge light bulb. If charge light illuminates when terminal ‘‘L’’ of harness connector is grounded, check IC regulator and positive terminal of diode.
If charge light illuminates with ignition on, start engine.
If charge light remains on or blinks, check fan belt, check ‘‘S’’ or
‘‘B’’ terminal for improper contact and generator output.
If charge light is off while engine idles, check voltage at
battery terminal while running engine at 1500 RPM. If voltage is 15.5 volts or greater, replace IC regulator assembly. If voltage is less than 12.5 volts, check IC regulator as a single unit. If voltage is 12.5-15.5 volts, turn light switch on while engine idles. If charge
light illuminates, check diode assembly. If charge light does not
illuminate, problem is not present.

I would think any decent service shop could find the problem..

[Beav]

One thing is for certain, if you don't fix it soon you'll be replacing a lot of light bulbs and possibly some very expensive components - ECU, TCU, control modules, etc. plus the battery will sulfate and turn to crap if left unrepaired.

99% of the time the high voltage rate is a shorted regulator allowing full ground to the field. The pulsing is indicative of a bad diode, this may be the cause of the regulator's failure.

[oab_au]

Originally posted by lee
1: Alldata says the Alternator should put out 14.2 - 14.8 Volts - I'm assuming that's at idle (or maybe 1500 rpm?).

2: Is 13.2 is correct at idle - isn't that about what the battery should show with engine off?

3: I always thought the voltage regulator's purpose to prevent overcharging, not regulating the volts themselves, not true?

4: I think I understand generators, and always assumed alternators were somehow the same excepting the need to rectify the current. I thought increasing the engine speed would produce more current, but not much voltage change - thinking somehow this was a basic physical property.

5: Anybody brave enough to take me through alternator 101, please PM me.

Seeing this is the Technical Section, I'll post it here.

DC and AC generation is the same, except for the rectification. DC uses brushes and a commutator, AC use diodes.

Voltage is produced by the windings of the coil, moving through a magnetic flux (or field). The more turns on the winding, the more magnetic flux , the higher the speed of rotation, the more voltage is produced .

As the speed of rotation is increased, so is the voltage increased. The current is controlled by the gauge of the wire in the coil and the potential difference across the coil.

The voltage regulator looks at the battery voltage and regulates it to a max of 14.7volts. It does this by reducing the current flow in the field windings on the rotor, thus reducing the magnetic flux and the charge rate.

If it was uncontrolled the voltage and current would rise with speed, till the windings melted.

The voltage in the system depends on the state of charge in the battery. Before starting the engine the battery voltage would be about 12.4, when it is running the voltage will rise, till the battery is filled and the voltage reaches 14.7 volts. You can't say what the voltage will be at a particular time, it depends on the charge in the battery.

You can't charge a 12 volt battery with 12 volts, a higher potential is needed to flow the current. Thats why we use a cut off of 14.7volts.

If everything is OK, the voltage will reach and run at about 14.7. Even with lights on, as long as the rotational speed is enough, like driving in third around town and no underdrive pulley.

Is this enough or is there a particular point you want cleared up Lee.?
Harvey.

[lee]

See if I got it. The voltage regulator IS regulating current like I thought, but it uses that current regulation to affect the change in voltage by altering the field, yes?

I couldn't see the voltage regulator (at least old primitive ones) regulating voltage as they were mostly a switch. And I couldn't see how regular diodes could regulate voltage either (not sure how a zener works - need to read more I guess). But if they are acting to regulate field current, then I think that makes sense to me again.

As long as I didn't translate wrong, then no need for a longer lecture - and thanks a bunch.

I can't always fix things myself, but it bugs the heck out of me if I can't grasp at least a little of how it works.

so just replace the alternator is what your all saying....I'm asuming the regulator is built into the alternator, correct?

[oab_au]

[QUOTE]Originally posted by lee
[B]See if I got it. The voltage regulator IS regulating current like I thought, but it uses that current regulation to affect the change in voltage by altering the field, yes?

>Yes thats right.<

I couldn't see the voltage regulator (at least old primitive ones) regulating voltage as they were mostly a switch. And I couldn't see how regular diodes could regulate voltage either (not sure how a zener works - need to read more I guess). But if they are acting to regulate field current, then I think that makes sense to me again.

>A zener diode is a one way diode, that breaks down, at a particular voltage, to flow current in the reverse direction, in a controlled way. The reg uses a small zener as a voltage reference.
A bit different to the big one on the finned heat sink under the steering head on the Norton. It is blocking till the battery voltage reaches 14.7v where it breaks down to pass all the voltage over 14.7 to ground.<

Harvey.

[lee]

thanks again Harvey,

and yes Everclear, the regulator is in the alternaor

[oab_au]

Originally posted by EverclearAtMSU
so just replace the alternator is what your all saying....I'm asuming the regulator is built into the alternator, correct?

Yes the reg is in the alternator. If they replaced the alternator and maintain that it is OK, Then get them to find the fault and fix it. It's a wiring fault for sure. (well 99% sure)

I disagree with Beav on the reg shorting, may be. Most electronic componets fail open circuit, which would turn the rotor current off.

Harvey.

well, I have the part, so i'm just going to put it in there myself. Along with redoing all the wiring that goes to the alt.

Anyone know where i can get a wiring diagram?

[lee]

here on the net