alternator overcharge

[dingo]

basically I have way high overcharge 15-16V. from what i have read on Bosch style'B' t he options are bad regulator or badly grounded regulator...this is the third regulator im on and same symptoms..so i assume therefore..that somehow im losing the ground

So regulator to Alt DF(green),D+(red), D- (brown)....i assume that the brown wire is grounded WITHIN the alt?

is it grounded thru a brush assy ? or simply to the case of the Alt ?

id like to figure this out before undertaking removal procedure


ok. i measured continuity between D- (brown wire) and case of Alt and it shows 0.1 ohm...so its all connected. My question is then, since the alt. is grounded to the engine block and chassis....why do they bother running a wire to the internals of the alt? why not bolt it to the case ?

[Amskeptic]

i assume that the brown wire is grounded WITHIN the alt?
is it grounded thru a brush assy ? or simply to the case of the Alt ?

ok. i measured continuity between D- (brown wire) and case of Alt and it shows 0.1 ohm...so its all connected. My question is then, since the alt. is grounded to the engine block and chassis....why do they bother running a wire to the internals of the alt? why not bolt it to the case ?

D- is fully grounded when off, but I believe it moderates the magnetic field in the rotor for output control when running. Yes, it would go through a brush. Alternator does need a good ground for the case as well.
Colin

[dingo]

thanks.

i found this:

* Alternators with type "A" circuits have an externally grounded field. One brush is connected to positive battery voltage, and the regulator switches between field and negative to control output.


* Type "B" circuits have an internally grounded field with one brush connected to battery negative and the regulator switching between field and positive to control output.

overcharge: The cause is usually a defective voltage regulator or poor regulator ground connection.

[dingo]

for those concerned or curious about the inner workings of the Alternator Voltage Regulator:

REGULATOR

The regulator has two inputs and one output.

The inputs are the field current supply and the control voltage input

The output is the field current to the rotor.


The regulator uses the control voltage input to control the amount of field current input that is allow to pass through to the rotor winding.


If the battery voltage drops, the regulator senses this, by means of the connection to the battery, and allows more of the field current input to reach the rotor, which increases the magnetic field strength, which ultimately increases the voltage output of the alternator.

If the battery voltage goes up, less field current goes through the rotor windings, and the output voltage is reduced.

[Amskeptic]

for those concerned or curious about the inner workings of the Alternator Voltage Regulator:

Thanks for this. I love how the laws of electromagnetism have been so useful .
Colin

[dingo]

i tried another Bosch regulator i had lying around...im still getting very high output 16V...with the occassional jump down to low, then back up to high

its a brand new battery...so that eliminates the possibility of weak or old battery being the cause


hmmm

[Amskeptic]

i tried another Bosch regulator i had lying around...im still getting very high output 16V...with the occassional jump down to low, then back up to high

its a brand new battery...so that eliminates the possibility of weak or old battery being the cause


hmmm

Something is completing the field circuit without the the regulator's consent, chafed wire? grounding between the rotor and the case? insulation failure in the windings? I had a rotor fail to ground that left the idiot light on when the engine was running and off when the ignition was on with the engine not running.
Colin

[dingo]

If the battery voltage drops, the regulator senses this, by means of the connection to the battery, and allows more of the field current input to reach the rotor, which increases the magnetic field strength, which ultimately increases the voltage output of the alternator.

so maybe the regulator is getting a False low-reading about the state of the battery, and thus tries to constantly increase output ??

my question is how to measure what the V-Reg is seeing, as opposed to 'what-is'

sort of like the feedback loop of vacuum leaks causing the 02 sensor to get False 'lean' and thus ask the ECU to richen

[Hippie]

B+ terminal on the reg is what it sees, IIRC.

[dingo]

Reg sees B+ ? how is that.?..it only receives D+, DF, D-

My idiot light behaves completely normally.

One test i have yet to do is: Volt drop between B+ Starter and B+ Alt..but it said to do it with engine idling and alt under load. But how do i access B+Alt ?? (whilst idling)

the D- is still a mystery to me...inspecting the innards of my spare alt, i see that D- arrives internally to a terminal that is soldered to the metal bracket which is bolted to chassis of the alt...which i assume is grounded to the engine block. Why not just grounded externally ?


ok..so it seems that B+ becomes D+ and that feeds batt. status to the reg, which in turn, after electrical extrapolation, sends its variable output V down DF to prompt alt. to produce its own varying output

[Hippie]

I mean D+ on most regs. Mine says B+ though I think. Anyway, the wire that charges to battery is what it looks at. When it goes high, the contacts slow their vibration and that cuts the average voltage/current to the field coil.

[dingo]

with Ign Off and Reg connected: D+ reads 0.0 V
with Ign On and Reg connected: D+ reads 1.1 V [ is this too low ?? i dunno]


with engine running, reg connected: DF reads 16V (approx)

[Hippie]

Again, only going by memory on the terminals, DF should read battery voltage when running. If it sees only 1.1 volts it will crank DF up to the maximum voltage trying to get the D+ output up to charging voltage. Sounds like the cuftoff function inside the reg is bad. Like an open diode. Assuming the ground to the regulator and alternator is good that is.

[dingo]

makes sense..tho ive tried 3 different regulators (not new ones...so the door of possibility is slightly open

how do i tell the difference between a 'good' ground and an 'ok' ground ??

edit: D- IS the ground...from what i can tell...thru the innards of the alternator, chassis, engine...a very circuitous route for no apparent reason.

I have tried adding a ground directly from reg D- to ground...makes no difference to outcome

[Hippie]

Mmmm 3 in a row with the same voltage readings? Tried grounding? Must be the Alternator then.