Over charging

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Mikes270dart

Mikes270dart

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On Saturday I annihilated my battery, it was a smoking leaking mess. Replaced the battery and checked the charging system and it was pumping out over 17v. So I thought it was the VR, bought on and installed being careful about getting good ground. Still same problem. The blue and green field wires even with the ignition off have battery voltage. I know that's not right. Wire shorted against power?. Ignition that is supposed to power alt works properly. Voltage took out my tac, haven't check everything out yet. Attached is the VR I used. Any Ideas. Thanks

VR.jpg
 
The blue wire to the VR must be broken somewhere in the harness. I had one here that had a broken solder joint near the bulkhead where all the blue wires are connected. I believe there was 4 wires soldered at that joint. Check the blue wire for power with Key on at the regulator. Follow it to where it lost power.
 
Make SURE you are not leading yourself down the wrong path.

Double check with a current drawing test LAMP instead of a voltmeter. If both the blue and green have power the alternator cannot charge. So I'm questioning your test results

Use a lamp (not led) AND meter to double check:

1...Disconnect green field wire at alternator. Check from the disconnected alternator terminal to ground. Should be dead with key off, should have battery power with key "in run."

2...Disconnect VR connector. Probe blue wire, should show same as 1. above

3..If test in 1 is OK, leave green disconnected, fashion a jumper clip wire from the disconnected alternator field to ground, and briefly operate engine. It should charge hard, more rpm, more charge. Now DISconnect your jumper and charging should stop. Turn key "off" and engine should stop. VERIFY that the blue the alternator is dead. IF NOT you have a harness short/ melt problem.
 
Keep in your mind how simple the system is. THE PATH

From the key, the "ignition run" wire runs out into the engine bay. THAT wire supplies ignition, VR, and alternator field. So a simple circuit, it supplies "everything."

Blue from the key goes to the alternator field, through the field, and the VR, via the green, controls "the amount of grounding" so to speak, to control charging.

VR gets power from the same blue circuit, ground, and the green from the VR goes to the field

MOST POPULAR cause of overcharge is bad VR or shorted brush holder at the alternator. DISconnect both field wires at the alternator. Check continuity to ground at the brushes. Should be open / infinity to ground.
 
Simplified circuit. Ignore the dotted lines marked "old"
Power comes in from top right, this is the blue "ignition run" from the key. Power goes to the VR and to one terminal of alternator field. The field is ONLY connected to the two brushes, it is a simple electromagnet. The "existing wire" at bottom going to the VR is the green. The VR controls grounding of the green to control output. You can replace that with a jumper to ground for testing. VR MUST be grounded.
old-to-new-regulator-jpg.jpg
 
What car?
What year?
What electrical modifications?
Did everything work correctly at some point?
What was the last thing you did to the car / electrical system prior to the failure?
 
Mikes 270…..pay attention here..!! These good folks including mattox and a few others helped me through a problem I had also. Great info here..!! Swingn’
 
Dana67Dart said:
What car?
What year?
What electrical modifications?
Did everything work correctly at some point?
What was the last thing you did to the car / electrical system prior to the failure?
Click to expand...
Yes. I would have said that except he mentioned the blue field wire. "So I guessed" it is 70/ later or converted
 
1971 Plymouth duster 340. Stock. Only changes a set of autometer gauges. Everything worked fine till 5pm Saturday
 
Two things to diagnose:
1. Damage caused by the power supplied at high voltage.
2. Initial cause of voltage regulation being bypassed.

Uncontrolled voltage occurs when the alternator's rotor is supplied power and the brush that should go to the regulator's control (via the green wire) is connected to ground. However there are other ways high voltage could be allowed by the regulator such as when it gets incorrect voltare information.


Mikes270dart said:
1971 Plymouth duster 340. Stock. Only changes a set of autometer gauges. Everything worked fine till 5pm Saturday
Click to expand...
Autometer gages. Are those in addition or instead of? I ask because old school set of 3 gages under the dash often included one ammeter, and in more recent times a lot of people add a voltmeter.

I think Del's post 4 is a good first step even if it seems redundant to your initial tests.

Mikes270dart said:
Replaced the battery and checked the charging system and it was pumping out over 17v.
Click to expand...
It may be helpful to consider that is more like pressure, and ampreage is flow. So the charging system was producing over 17 Volts. The amount of curent it was pumping out is what ever was shown on the ammeter, plus whatever was going to the ignition and alternator's rotor. Factory stock, that would be about 5 amps at 14 volts and a more at 17 volts.

This may seem picky, but I think understanding it is helpful in diagnostics.
Mikes270dart said:
The blue and green field wires even with the ignition off have battery voltage. I know that's not right. Wire shorted against power?. Ignition that is supposed to power alt works properly.
Click to expand...
Not sure what you mean here by "works properly" if there is power in the blue wires with the key off.
Maybe recheck as suggest in post #4
Mikes270dart said:
Voltage took out my tac, haven't check everything out yet.
Click to expand...
High voltage could take out any electrical item that was switched on.

I'd examine all the connections and wires from the alternator output to anything that was drawing power.
 
At minimum it would be worth visually checking these connectors for damage.

1692967022025.png
 
Mattax asked: Autometer gages. Are those in addition or instead of? 2 gauges installed Water temp and oil pressure.
Not sure what you mean here by "works properly". Up till that point I never checked for proper power on blue wire.

Cant do anything this weekend, will start Monday unwrapping and checking wires, Connections Etc.
Thanks
 
OK, those gages shouldn't effect anything.
Hopefully you won't have to unwrap harness.
Disconnecting the bulkhead connectors requires a little patience wiggling while holding the release catches back.

As you can see from the drawing. circuit wures A1, R6, J1 are all connected together.
J1 (power into the ignition switch) should connect to J2 (ignition run) only when the key is in run.

Current should flow thorugh the alternator's rotor like this.


1692994629833.png
When the volrage sensed by the regulator is below approximately 14 Volts.
 
Seems that my previous post had some errors. Also some reading from last night make no sense. with Blue and green wires disconnected from the alt both post read ground with test light connected to + side of battery. With key on blue wire has power and green stays ground. Both the green and blue wires are good to and from the VR.
 
Mikes270dart said:
Seems that my previous post had some errors. Also some reading from last night make no sense. with Blue and green wires disconnected from the alt both post read ground with test light connected to + side of battery. With key on blue wire has power and green stays ground. Both the green and blue wires are good to and from the VR.
Click to expand...
Sorry Mike. I know your trying but I'm having trouble understanding what you did.

a. You disconnected the field wires from the alternator.

b. Then connected a test light from the battery positive to each field terminal on the alternator ?

c. Connected a test light between the blue wire's field connection and ground, and it lit with the key turn to run.

d. Somehow determined the field wires are 'good' What was the test or check ?
 
Somehow determined the field wires are 'good' What was the test or check ? Used an ohm meter on the wire to check
You disconnected the field wires from the alternator. Disconnected the green and blue wires from the alt
Connected a test light between the blue wire's field connection and ground, and it lit with the key turn to run. To check for power on the blue wire with key on
Then connected a test light from the battery positive to each field terminal on the alternator. not sure what i was trying to prove with this(checking grounds) but found it interesting that both male connectors on the alternator fields signaled as ground. maybe means nothing.
 
Mikes270dart said:
Somehow determined the field wires are 'good' What was the test or check ? Used an ohm meter on the wire to check
Click to expand...
Continuity with an ohm meter means just that, and only that.
In other words, there is continuity between two points. If it shows measureable resistance, then there is continuity but its not good enough to do the job it needs to do.
If it shows no more resistance than touching the two probes together, then its probablyt OK but might or might not be good.
What I'm saying is if there is one strand of copper connected, there is still continuity, but there will be resistance to current flowing through.

Mikes270dart said:
Then connected a test light from the battery positive to each field terminal on the alternator. not sure what i was trying to prove with this(checking grounds) but found it interesting that both male connectors on the alternator fields signaled as ground. maybe means nothing.
Click to expand...

If both field wires were removed from the alternator, then the field circuit has a short to ground.
See Identifying Chrysler Alternators (1960-1976)

This may explain the uncontrolled alternator output.
If the brush connected to the run circuit is properly insulated, but the brush to the regulator control is grounded, then the rotor will be fully powered, full time.

In contrast if the wire from the run circuit was connected to ground, then the rotor would get no power but battery would dump maximum current to the ground short until something melted. The ammeter would show major discharge until the connection was broken.
 
Mattax said:
If the brush connected to the run circuit is properly insulated, but the brush to the regulator control is grounded, then the rotor will be fully powered, full time.
Click to expand...
Illustration of how current will flow with an isolated field alternator when the brush that should connect to the regulator is grounded.
1693325520329.png


Here's my suggestion.

Key off.
Field wires disconnected (wires J2 & R3)
Use the ohm meter. Touch probes together to check for resistance. write that number down. Or if its an analog meter, zero it with the compensator dial.
Place one probe on the alternator housing. (Clean for good contact if needed)
Place a probe on each field terminal. Write down the resistance.
Then place the other probe on a field terminal. Write down the resistance if any.
Move that same probe to the other field termianl. Write down the resistance if any.

Possibility A
If there is continuity, zero or measureable resistance between either field terminal and ground, that is a fault.
If so, Remove the alternator.
Remove the brushes. Measure the resistance between the slips, and then each slip ring and ground using the same procedure as above.
If the slip rings have no continuity to ground, the fault was in the brush and terminal insulations. Replace them.
If the slip rings have continuity to ground, there is an internal problem.

Possibility B
There is no continity, infinite resistance between the field terminals and ground.
Short to ground must be in the R3 wiring or regulator.
 
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Ok, touch probes together no resistance. Put a probe on each male tab on the alternator no resistance. From the tab where the blue wire went to case no resistance and same for green.
As a side note after giving the tab where the blue wire goes, plugged in in an put key to run. It does get hot.
Thanks for your help
 
Didn't have time to properly troubleshoot alternator so I bought a rebuild, now the charging system works the way it should.
Thanks again.
 
The ALT was the problem in the end..?? Hopefully your back to normal..13.8-14.5..?? Swingn’
 
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