Alternator regulator operation


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Alternator regulator operation

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discretesignals
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Jan 15, 2012, 4:57 PM

Post #1 of 7 (2535 views)
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Alternator regulator operation	Can't Post

Hi there,

I'm a mechanic and trying to solve a problem on a customer's vehicle. The charging system isn't operating on this vehicle. I know this is a tv repair forum, but most of us mechanics don't really get into solid state repairs. We read what is going on in the component in question and how it is controlled to figure out if the component is bad or not after testing outside the box. The problem I am having is understanding how this alternator's regulator's circuit operates. The service information is vague and doesn't give you any input or output voltages or signals to go on. Just curious if any of ya know what is going on in this circuit.

Here is the schematic:

I do understand the functions of the components in the alternator, but as to how the regulator is controlling the field coil to regulate the alternator's output is beyond my level.

I can tell you when the engine is running, the voltages on the pins for the alternator's connector are:

PIN 2 Orange wire 12 VDC
PIN 1 Blue wire .5 VDC
PIN 3 Grey wire 12 VDC
PIN 4 Pink wire 12 VDC

If the blue wire is back probed, there is a reading of 8 VDC. This was taken from an operational charging system.

I appreciate any information on teaching me what is going on in this thing... Smile

Ron.M
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Jan 15, 2012, 8:44 PM

Post #2 of 7 (2529 views)
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Re: [discretesignals] Alternator regulator operation [In reply to]	Can't Post

discretesignals;....

1st off , I'm guessing that that circuit board is inside the alternator...Correct ???
If so , just change the alternator...
Does that 10 amp fuse (Top left corner) show 0.0 ohms whern you read it ???
Are you reading 0.0 ohms from the fuse to where it says "sensing" on the schematic ???

As a mechasnic , you know that a good alternator puts out 14 vdc when running...
IF you are not getting that , then the alternator's bad....Simple, no ???

Later...Ron.M.... Cool

....
Veteran & Retired TV technician

discretesignals
New User

Jan 15, 2012, 9:00 PM

Post #3 of 7 (2524 views)
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Re: [Ron.M] Alternator regulator operation [In reply to]	Can't Post

Hey Ron,

The solid state components (transistor, diodes, resistors, etc.) are inside the regulator which is inside the alternator case. Looks like this:

The alternator was replaced. The new alternator was bench tested and found to be operational.

The fuse shows zero ohms and there is battery power on the circuit the fuse protects at the alternator's connector. Everything is there at the alternator except what is susposed to be coming from the PCM. The service information doesn't give us a clue as to what the PCM is susposed to be sending or recieving from the alternator.

I thought by finding out how the regulator works based off the components in the schematic, we could figure out what the alternator is looking for from the PCM (engine computer). Our service information doesn't provide this information in the description of the system or the trouble charts. I thought maybe you guys/gals would have some answers because you deal with solid state equipment and repairs.

Ron.M
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Jan 15, 2012, 9:33 PM

Post #4 of 7 (2519 views)
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Re: [discretesignals] Alternator regulator operation [In reply to]	Can't Post

discretesignals;....

Can not get circuit (Regulator) pix to go to thread....

The unit looks like it's a sealed unit & can not be repaired....
Have you tried a new one ???
I probably could try to explain the circuit , but that isn't going to help you much...

From what I see , IF you are getting 12 vdc on pin #2 & 0.5 vdc on pin #1 then that circuit should be putting out 14 vdc....
Usually in TVs etc , it takes 0.6 vdc to get a transistor going....
NOT always....In this case 0.5 may be what it's designed to operate on....

On the schematic there's a connection marked "Battery"....
You should get constant 14 vdc on that pin on the regulator....
Read volts there & see what you get....
IF 12 vdc , replace regulator circuit...

Also you might want to see if the 120 amp fuseable link going to the battery is OK...

Pin #3 is most likely for a dash board indicator lamp...
Pin #4 , I think is for "test" when the ignition switch is in the ACC position....
Make sense ???..

EDIT;...

Quote

If the blue wire is back probed, there is a reading of 8 VDC.

Don't quite know what you mean by "back probed"...
care to explain ???

Have fun.... Unsure

.....

Later...Ron.M.... Cool

...
Veteran & Retired TV technician

(This post was edited by Ron.M on Jan 15, 2012, 10:37 PM)

discretesignals
New User

Jan 16, 2012, 1:45 AM

Post #5 of 7 (2509 views)
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Re: [Ron.M] Alternator regulator operation [In reply to]	Can't Post

Thanks for your time in answering this thread.

From the knowledge of alternator 101 this particular alternator has to be excited to begin functioning. It gets excited by the lamp circuit through that pre excitation resistor and lamp bulb. Once excited the stator produces the voltage to the regulator to keep the alternator charging. The regulator is new with the alternator or proved to be good during bench testing. I'd like to see how they benched test it. I can only guess that they full fielded the alternator some how.

The amount of current that flows through the rotor coil controls the output of the stator. I believe the rotor's current is controlled by TR3 in the regulator. TR2 is what grounds the lamp circuit to turn on the alternator lamp. I don't know what TR1 is doing or those diodes including the zener. I know that diodes are one way check valves and a zener is a diode that blocks current flow up to a certain point.

I just can't wrap my brain around it to really understand how the regulator is actually functioning. Most of us mechanics understand from reading what a dotted box in the schematic does and can measure signals and voltage from it to get an idea what is going on inside it, but when we look at its circuit board schematic we are lost to how current is being manipulated to get it to do what is wants it to do.

The service information says that the PCM monitors the amount of current change when loads are put on the alternator (cooling fans, ac compressor, etc.) from the FR circuit (blue wire) and uses the G (ground) circuit to control alternator output.

The service information doesn't say what these values should be or what a waveform pattern should look like. We really need to get hold of an oscilloscope and monitor these signals to see what they are doing on a good vehicle.

You guy/gals may call it something different, but back probing is usually done to the back of a connector, so you can measure a circuit without disconnecting the circuit or piercing the insulation.

(This post was edited by discretesignals on Jan 16, 2012, 1:50 AM)

mel
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Jan 16, 2012, 2:52 AM

Post #6 of 7 (2503 views)
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Re: [discretesignals] Alternator regulator operation [In reply to]	Can't Post

If this is a Chevy, seems to me that some time ago the fusible link failed in my Chevy. Being a shade tree mechanic on my own vehicles, I had a heck of a time even finding it

Ron.M
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Jan 16, 2012, 8:28 PM

Post #7 of 7 (2496 views)
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Re: [discretesignals] Alternator regulator operation [In reply to]	Can't Post

discretesignals;....

1st , I need to clear up something , then I'll give you some info from Basic Electronics 101 which may enlighten you & correct some errors in Alternator 101.....

Concerning;=>...

Quote

If the blue wire is back probed, there is a reading of 8 VDC. This was taken from an operational charging system.

WHERE are you reading 8 VDC at ???...& HOW ???
&

Quote

PIN 1 Blue wire .5 VDC

Pin #1 on your schematic goes to the base of TR1...
(That schematic may not be entirely accurate)..
TR1 appears to control TR2...
TR2 appears to be controling TR3 & turns the lamp on & off...
TR3 is the transistor that provides current for the rotor coil...
The more current thru the rotor coil , the higher the output at "battery" connection , giving you a higher charging rate...

The 0.5 vdc coming in on Pin #1 IS your control voltage for the rate of charge..
If & when it changes , the rate of charge changes...

I have some reservations as to how the alternator was tested...
Bench testing , to me , means the alternator is capable of charging a battery...
That , again to me , does not prove that the regulator circuit IS working...
I am concerned with the voltage on Pin #1...
IF the battery is low & needs charging , I would think that that voltage would change...
Your problem could be the PCM is not working properly...

Quote

I don't know what TR1 is doing or those diodes including the zener. I know that diodes are one way check valves and a zener is a diode that blocks current flow up to a certain point.

TR1 already explained.....
The zener allows a set voltage to pass thru...
In this case it apparently is set at a level that when the voltage from TR1 goes higher than what the zener is designed to handle , it passes that to TR2 which in turn conducts...
When that voltage drops to a level that the zener blocks it , TR2 is turned off & your lamp is turned offf...

Quote

The service information doesn't say what these values should be or what a waveform pattern should look like. We really need to get hold of an oscilloscope and monitor these signals to see what they are doing on a good vehicle.

I personally do not think a "scope" is going to be of any help...
Reason is that you are working with DC voltages & scopes are designed to show AC signals...
All you'll get with DC is a flat line possibly with a little ripple that could be used to measure DC volts...

Quote

The service information says that the PCM monitors the amount of current change when loads are put on the alternator (cooling fans, ac compressor, etc.) from the FR circuit (blue wire) and uses the G (ground) circuit to control alternator output.

Some identity confusion here....
According to your info , the "Blue" wire goes to Pin #1....("PIN 1 Blue wire .5 VDC" )...
It is marked as "C" or "G" on the schematic...
It is NOT "ground"...
It IS the control line from the PCM...
The metal case that all this is in is the "Ground"...
The "FR" line is pink & goes to Pin #4...("PIN 4 Pink wire 12 VDC")

IF you read 8 vdc on Pin #1 on a car that has a working charging system & 0.5 vdc on a car that is not charging , then the obvious conclusion is that possibly the PCM is at fault...

GOOD LUCK..... Sly

....

School's out.... Smile

....

Have a GREAT day & week.... Sly

....

Later...Ron.M.... Cool

....
Veteran & Retired TV technician

(This post was edited by Ron.M on Jan 16, 2012, 8:30 PM)

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