big volts

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barbee6043 said:
I made 2 changes earlier today. I put a fresh battery in it, and replaced the starter relay, ( told in previous thread this can cause elect. problems).

I turned on the lights, heater motor, moderate to fairly high reves, readings: batt + : 12.2 alt. output stud 12.1 , and at idle : batt + 12.2 alt 11.9
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If those reading are correct then the alternator is not charging. When the alternator is charging the voltage at the output stud should be higher than the engine off battery voltage. It sounds like the car is running on the battery only. If the voltage regulator is only seeing about 12 volts on the blue wire it should be increasing the alternator field duty cycle to increase the voltage.

Here is what I would do. Hook your meter to the battery and note the voltage reading with the engine running. There should be two small field wires on the rear of the alternator, one dark blue and one green. With the engine running test the blue wire to be sure it is essentially the same as voltage at the battery. Then test the green wire and note the voltage. It should have some voltage greater than zero, typically between 4 and 11 volts depending on engine speed and electrical load. These are the wires that come from the voltage regulator. Test at the alternator, not the regulator.

Almost forgot, a fully charged battery should be at 12.6 to 12.8 volts with the engine off. Substantially less than that means the battery is discharged to some degree.
 
Yeah, around 12.7 volts is good. Earlier I posted 13.2 volts for full charge, which after some research,I discovered is the nominal charging voltage, not the normal battery rest-voltage. My mistake. Sorry.
 
I will check these reading tomorrow rustedwrench......its been a LONG day today!!!! I took the alt to O reillys checked O K there ( if that means anything!!)..... the VR is new but perhaps Bad or not correct for this car!????

I/m glad the tornado headed straight for us last night dissapated a few miles before it got here!! 3-4 twisters hit in s w Mo but no one killed. that's good!
 
Rustedwrench said:
If those reading are correct then the alternator is not charging. When the alternator is charging the voltage at the output stud should be higher than the engine off battery voltage. It sounds like the car is running on the battery only. If the voltage regulator is only seeing about 12 volts on the blue wire it should be increasing the alternator field duty cycle to increase the voltage.

Here is what I would do. Hook your meter to the battery and note the voltage reading with the engine running. There should be two small field wires on the rear of the alternator, one dark blue and one green. With the engine running test the blue wire to be sure it is essentially the same as voltage at the battery. Then test the green wire and note the voltage. It should have some voltage greater than zero, typically between 4 and 11 volts depending on engine speed and electrical load. These are the wires that come from the voltage regulator. Test at the alternator, not the regulator.

Almost forgot, a fully charged battery should be at 12.6 to 12.8 volts with the engine off. Substantially less than that means the battery is discharged to some degree.
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all this started when I noticed I was getting 18-19 volts reading the the VR. I assume I should have checked those reading then at the alt. but that I didn't know. I installed new VR, starter relay ( it was working fine but obviouslyold), fresh charged battery. I took the alt to o reillys checked O K. I did full field test 2-3 times charging ( I forget exactly but seems like 16-17???.

just while ago, with fresh charged battery, I warmed the enogine and got these readings: running at idle...... batt + 12.7 med. to fairly high rpm meter bounces fro, 12.2 -12.9 alt big posy gr to alt body 12.2 the green alt wire 8.8 blue alt wire 11.4

I unplug the wires at V R and green wire jumps from like 14- 15. and the BLUE wire there bounces 1 to 19 then nothing????????????

so do I need to jump from the alt blue wire post and splice at VR and see what happens????????? thanks for the help....
 
I went through this recently with my Valiant. My problem was insufficent/deteriorated grounding between the engine and the body.

I cleaned the existed grounds and added the factory braided ground wire between the head and firewall and problem solved. Don't know where that cable disappeared to over the years.
 
I cleaned the batt neg to eng block, the wire from block to firewall and the second batt neg to rad support!!!!!! did that at the very beginning.
 
AJ/FormS said:
cause the key is on.
If you are only getting 12vdc at the output stud of the alt, and reading 12.5 at the battery, then the alt is no longer charging. Now it may be that its defective/broken or it may be that the field circuit is not working.

"with just key on, I get 12.5 at batt... ballast l is 11.6 both terminals, .. at the VR I get 11.6 out of both the green and blue wire there. why would I get any reading at the green field wire at the VR ?"

Because that is a series circuit. The battery voltage is coming through the ig sw RUN down the blue wire to the VR,to the alt field coil,out the coil to the green wire ,and back to the VR.There will be a voltage drop from end to end, but its all one long string.
In a perfect system, with the engine not running, there would be the same battery voltage every where throughout the system.(except for certain dash gauges.)
In a perfect system, with the engine running, there would be regulated alternator output every where throughout the system.
The battery voltage is very nearly always below the VR set-point voltage. So right after you start the car,and the alt is fired up by the ig sw through the VR, it begins to pump out DCvoltage. It pumps it out hard, every where, and it only takes a moment to get to the VR down the blue wire.The VR says whoa there buddy, thats too much.It then immediately starts leaking what ever voltage is higher than the set-point.It leaks it from the green wire to ground.As soon as the voltage drops below the set-point the VR stops leaking, and the blue wire voltage rises. Thus it regulates the system voltage by varying the field leakage.The VR set point can be anywhere from a low of about 13.2 to a high of about 15.2. It varies by manufacturer.As a very general rule, on our classics,the charge voltage runs about 13.2 to maybe as high as 13.8. And thats about what you should be seeing everywhere except on the coil side of the B-resistor.Here it should start out near that same reference voltage, when its cold, and the voltage should drop as it heats up. Which doesnt take long.
So thats why the VR case has to be well grounded; so it can leak. And why the alt has to put out DC voltage, so the VR knows whats going on. And why the VR needs to see battery voltage at the blue wire.
High resistance connections anywhere in the system between the battery and the alternator, can fool the VR into thinking it ought to leak less and therefore puts out more voltage.
Do you know how to perform a full-field test? You will need to perform one on your alt to prove its good or not. Also you will need to check it for A/C output.
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I've done the full field test several times. just did it again. motor reved, 18.5 at aly outpu post, 17.5 at batt +.

it did this while ago, engine idling if I remember ( remember HA!).. with the green wire OFF ... the alt. the blue wire terminal showed 11.8 then I the blue wire off and probed the end of that blue wire, 15.2

with the blue and green wires on their terminals, and engine REVED I get 9.1 at blue wire term and 11.6 at green wire term ( hard to read my writing!!????)...

I havn't got into the dash wiring to try to check V in there. I was hoping the problem to be under the hood.

if I pu the blue wire off the V R and get no reading the problem is somewhere between there and bulkhead connector and maybe on inside the dash somewhere right???????


I think maybe in a previous life I fried myself with electricity and NOW reincarnated ,, that's why auto elect. is like Greek. ( I speak NO Greek).. LOL
 
further underhood checking. I havn't had time or energy to pull the instrument cluster out to check wiring in there. but this is what i'm finding ub=nder hood now. the volts where the fusbilbe link wire goes to bulkhead reads 12.4 same as batt +, starter relay stud, and alt stud ( actually 12.2)....... the big hot wire coming out of bulkhead was reading 16.8-17.5....... from what I read from you guys this should be 12.4 ???????????
all this is at slow IDLE

o k..... the green an blue wires at the alt show 8.0 ands 11.4...

I pull the wires off and check at V R....... green 14.4 and the BLUE again I s bouncing all around 1 to 19 ............. this is not normal from what I read here????????????

earlier I couldn't get a rading at the blue V R wire. I have to really rub the probe there hard to get a reading and like I say it bounces from 1 to 19...............

so 2 questions: should not I have the same volts in and out of the bulkhead????? what causes this????????????

and this blue wire at VR bouncing all around from 1 to 19 V? bad connection, new new??????

thanks for the help!
 
you have no idea how this works, do ya?

try to follow a plan, like, just like driving down the road. where does it start where does it go?
 
In and out of the bulkhead,Yes.
-With the engine off,key run,the headlights and heater off,and the blue wires off: (the alt, the VR, and the B-resistor), Battery voltage should be everywhere about the same. That would be; the A1-10Red circuit that goes from the battery to the ammeter, the R6-12Blk circuit that goes from the ammeter to the alt output stud, and every open circuit blue wire if/when the ig sw is in run.And every blue wire should drop to zero with key off.
-With engine off,key in run;As each disconnected item is reconnected expect the voltage to drop a bit, until you get to the alt. Here disconnect the green wire from it first. the when you reconnect the blue to the alt, there should be very little change in the voltmeter.Then if you ground the terminal where the green wire came off(full fielding it), the voltage should drop quite a bit, as the armature sucks up electrons from the battery. Then as the battery recovers the voltage might pop back up a bit.Do not leave the green wire grounded longer than necessary to complete the test. A few seconds is all you need.
-So thats the yes answer.

Now, if you again disconnect the VR and the alt field wires, and then start the car; the voltage should again be everywhere about the same as measured on the supply side of the devices, and be battery voltage.Then when you connect the VR to the blue(green off the alt), expect a small drop in voltage, and with the green still off the alt, no change when the blue is reconnected to the alt.At this point the engine is running 100% on battery power.If you were to turn on the lights or/and heater at this time, the voltage would drop everywhere to a new level but nearly the same throughout the system(the alt is not yet on line).
-Ok so, lights and heater off, lets reconnect the green wire to the alt.Now, if the VR is good and has a good ground, it should immediately pump the voltage up to its set point, which could be in the neighborhood of 13 to 14 or more volts.It does this by grounding the green wire.As the senses the voltage rise at the blue wire, it shuts off the alt, which causes the voltage an the blue wire to fall, which the VR again sees, and turns the alt back on. It does all this seesawing so fast that the analog meters never catch it.They will just read the average voltage. It will be seesawing between battery rest voltage and its set-point. It could be between 10 or 11 volts on a really flat battery and the set-point, or as the battery comes up, it could be switching from 12 or 13 volts to its set-point.If you have a digital VOM it probably wont catch it either.

-Now as to the large voltage spikes.I dont understand them either.The full field numbers are good, with a 1 volt drop from alt to batt. That same or similar drop should show up on the blue wire, anywhere along its length on the supply side of any device.
-The only thing I can figure is that the alt is pumping out an A/C spike and your meter is catching it, cause remember;during full-fielding, the VR is out of circuit. If that were true, then the alt is bad, having at least one perforated diode. But that alt was tested and passed. So I just dont know. I have a box full of used alternators here. I would be trying a different one, and retesting.
-Well, a thought just occurred to me. If there was an intermittent short, or a regularly pulsing high-current draw, anywhere in the electrics, the VR could be responding to it, by rapidly turning the alt on/off, full-bore. There is only one device that fits that description; the ig coil. I would think the stock coil would be too feeble to do that, and the B-resistor should damp it out.Youre not running an MSD are you?In either case these devices could only evoke a spike while the engine is running.
IDK Barbee. This is as tough as it gets.

PS; since your not calling out circuit codes,colors or wire sizes, Ima guessing you havent yet extracted these circuits from the wiring diagram. I think it would be really advantageous to you if you did. If I had a way of posting it for you I would. I tried to create something with the keyboard, but it turned into crap when I previewed it.
 
DDodger said:
you have no idea how this works, do ya?

try to follow a plan, like, just like driving down the road. where does it start where does it go?
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LOL... yes admit after decades I should understand way more of auto electronics than I do. I didn't used to have so much trouble. I admit to having catarac that I will fix next year. dyslexic. I have always inverted numbers, letters, all around, but I made it they 4 years of college and got a degree in Ag ( not rocket science!) LOL whats funny is, when I started college at a jr college, I took a course im farm electricity. I passed BUT never really understand half of it. go figure! LOL

I do have a FSM for the 65 dart. can hardly read it. I have no computer printer and I won't download factory diagrams. so I struggle along.

I do appreciate the people on here that take the time to try to give good advice and educate people like me. it its great for someone to take the time to do so... I say thanks you guys...

yes I do understand the hot wires go in and out of the bulkhead..... I found it totally weird my meter showed 12.4 going in and 16-17 coming back out...

I will do more diagnosis this afternoon. I will get it eventually!!!!
 
DDodger said:
rest of us cant see what you are seeing. we don't know what you are actually measuring
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I have to admit when I typed that I was tired. I was talking about the red hot ( fusible link protected ) wire feeding the firewall and the black hot one coming back out. had other things to take my time, will be a day or two before I get back to it.
 
"... I see no readings from the VR case."
This makes no sense. There must be a voltage reading. Do you mean you measure 0 V from VR case to BATT-? If so, that is good.

Did you try the "full field" test yet? That may determine if your alternator is OK.

You should not read a 3 V drop from BATT+ to the VR sense wire (blue). Was this another decimal point error? If true, the VR would think the alternator output is 3 V too low and command more (by increasing the voltage drop across the field), but your concern is not "voltage too high" (a more common problem).

It sounds like you have negligible voltage drop from alternator case to BATT- (good). But go back and measure that directly just to insure.
 
You are going to HAVE to get / buy/ make some wiring diagrams that you can understand. I've posted this before but the general "idea" on the big current side of the alternator is right there at Mad Electrical

Divide the problem up

It makes no sense to take readings if you don't explain exactly where you take them so the guys on this site can see and visualize what you are doing and under what conditions, IE warm, running, running fast enough to charge, with /without lights or other loads

Generally, the troubles.

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.........high voltage.......

If the high voltage is only at the alternator output, but low at the battery, this, generally, is going to be in the "high current" or output side of things. This includes the terminal on the wire right there at the alternator, the terminals feeding INTO the interior through the bulkhead, the AMMETER terminals, the WELDED SPLICE (see mad electrical and your diagrams) and the current coming back OUT through the bulkhead and feeding the battery via the starter relay stud.

The DIFFERENCE in voltage between battery and alternator STUD when running and charging, can be probably as much as 1/2 volt when running "hard," depending on condition of the various terminals

It it is substantially more than 1/2 volt, you probably have a bad connection in the "path" from alternator output to the battery. This includes the bulkhead terminal large red and large black wires, and the ammeter, and under--dash welded splice. Refer to the Mad Electrical site

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SHORT causing "full field" output. This occurs some on 70 and later vehicles with "dual field" that is correctly "isolated field," when the GREEN field connection becomes GROUNDED. This is the field wire leading off to the regulator, and in 70 and later, the green sort of controls "the amount of ground" on the field. The field in 70 is FED power from the ignition switch (blue.) So if that green circuit gets grounded it will charge full output and high voltage

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POOR GROUND on the regulator. This is not simply "tightly bolted." This means the entire pathway, through the regulator flange, bolts, to the body, the jumper ground (where ever it is) to the engine block and back to the battery. The VR MUST be grounded at the same voltage (potential) as the battery.

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BAD REGULATOR. Rare, does happen sometimes I assume you've already tried a different one

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VOLTAGE DROP in the ignition circuit. I've preached and preached. If there are poor connections in the "feed" to the VR ignition terminal, IT WILL charge "over voltage."

The "path" on factory wired cars is

from battery....to starter relay....through bulkhead on red ammeter wire----to ammeter---to welded splice under the dash------to ignition switch connector--------through switch--------back out switch on IGN 1 wire-------back out bulkhead on IGN1 wire---------and to feed off to underhood ignition loads, including

ignition system

alternator field (blue) on 70 and later

regulator IGN terminal

smog stuff on some cars, and electric choke if used
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The above is the "ROAD MAP" I've so often preached. Wiring is exactly like driving down the road. Some of the road is wide (big wire) some of it has potholes at poorly marked intersections (splices and terminals) and some of it branches off on unmarked roads (circuits you are unaware of and confused by)

So just like "going somewhere" you need this road map, and you must go DOWN that map one mile at a time

I've posted numerous stuff on this, do a search.
 
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