Doesn't seem to be charging properly

[MaximRecoil]

This is a 1969 318 automatic. I converted to a newer style alternator and electronic voltage regulator (see this thread). When I finished with the conversion, with the engine running it was showing 13.8 volts at the battery terminals, which means it was charging fine. Today however, it didn't seem to be charging properly. Sometimes it would show about 12.5 volts at the battery while running, and other times it would get up to about 12.9 volts. To get up to 12.9 volts, it has to be charging somewhat, perhaps intermittently, but it doesn't seem right.

I'm showing good continuity between the electronic regulator's outer metal case and various ground points on the car (e.g., engine block, firewall, negative battery terminal), so that's not the problem.

The car's alternator gauge seems to be showing intermittent activity. While idling, sometimes the needle stays dead center, and other times (usually when I rev the engine, but not always), the needle advances to the right some.

I followed this wiring scheme:



From this site.

One thing I wondered about when rewiring it: on the stock mechanical regulator setup, there were two wires that went into the quick-disconnect terminal that pushed onto the driver side of the voltage regulator (ignition terminal):



Now, according to the instructions and the diagram, you remove the wires that connect to the old mechanical regulator and splice them together, and also splice in the center wire of the new plug. The instructions only mention two wires (ignition and field, for a total of 3 wires being spliced together when you add in the center wire of the new plug), but I have 3 wires there, 2 going into the ignition side and one into the field side. So I ended up splicing a total of 4 wires together (the 3 that went to the old regulator plus the center wire of the new plug). Was that the right thing to do?

I've heard that the car's alternator gauge is a critical part of the charging circuit, so if something is screwy with that, it won't charge properly. I was thinking about adding a jumper wire across the two terminals of the gauge to eliminate that potential problem (any thoughts on this?). Are there any other parts of the charging circuit I should test?

[nascarxx29]

The 2 blue wires that formally went to the old black box regulator get spliced into this type newer plug
http://www.bouchillonperformance.com/BPE5312.asp

[MaximRecoil]

The 2 blue wires that formally went to the old black box regulator get spliced into this type newer plug
http://www.bouchillonperformance.com/BPE5312.asp

I don't know what color the wires are, but I had 3 wires that went to the old black box regulator; 2 of them factory-crimped into a single quick-disconnect terminal that plugged on the ignition side of the old regulator, and one with a factory-crimped spade terminal that went to a screw terminal on the field side of the old regulator.

I spliced all 3 of them and the center wire of the new plug (the blue wire in the picture you linked to) together. I also ran a new wire from the outer wire in the new plug (green wire in the picture you linked to) to the negative field terminal on the alternator.

[nascarxx29]

The old black box regulator had a push on double blue and a screw on single green wire .Follow the diagram your changing the 70 and up voltage regulator type plug using same color wires
http://www.mymopar.com/downloads/Dual_Field_Alternator_Wiring.jpg

http://www.mymopar.com/downloads/1970/70ChargerA.JPG

[MaximRecoil]

The old black box regulator had a push on double blue and a screw on single green wire .

Yes, and I spliced all 3 of those plus the blue center wire in the new plug together (for a total of 4 wires spliced together). I need to know if that was correct or not, because all the instructions and diagrams I've seen only mention 2 wires going to the old regulator, when there are in fact 3 wires going to it.

Follow the diagram your changing the 70 and up voltage regulator type plug using same color wires
http://www.mymopar.com/downloads/Dual_Field_Alternator_Wiring.jpg

http://www.mymopar.com/downloads/1970/70ChargerA.JPG

I followed the diagram that I posted above:



But there was that extra wire that the diagram doesn't mention. Was I supposed to splice them both in with the green (field) wire and the blue center wire of the plug, or only splice one of the two in with them and leave the other one just hanging?

[b5blue]

Is you ignition stock points or modified? 

[Plum Crazy 68]

Be sure to clean all your grounds and terminals, and make sure the grounding strap is there. 

[nascarxx29]

As said the alternator and voltage regulator require good grounds to work correctly.If you search this term in the search box[not charging] you find many that had that problem and how its was resolved

[MaximRecoil]

Is you ignition stock points or modified? 

Stock points.

As said the alternator and voltage regulator require good grounds to work correctly.If you search this term in the search box[not charging] you find many that had that problem and how its was resolved

The grounds are good.

I still need to know if I have it wired correctly.

Yes or no: All 4 wires should be spliced together (2 from the ignition side of the old regulator, 1 from the field side of the old regulator, 1 from the center terminal on the new plug); like so:

[b5blue]

  Though I'm not certain, it looks like you may have the "start" (Full 12 volts) and "run" (12 volts run through resistor) of your ignition wiring tied together? That would burn up your coil sooner or later. (I have no idea what effect it would have on charging.)  I always sand rusty sheet metal to bare shiny steel and coat it with dielectric grease on any contact ground point. (I have a 70 with a ECU type ignition harness so I'm not much good on the retrograde your doing.)

[MaximRecoil]

 Though I'm not certain, it looks like you may have the "start" (Full 12 volts) and "run" (12 volts run through resistor) of your ignition wiring tied together? That would burn up your coil sooner or later. (I have no idea what effect it would have on charging.)  

On the original electromechanical regulator, there were two terminals: field and ignition. The field terminal (which was specifically a screw terminal) had one wire going to it. The ignition terminal (which was specifically a quick disconnect terminal) had 2 wires going to it.

The diagram that I've posted a couple of times says to splice the field and ignition wires from the old regulator together, along with the center wire from the new regulator plug. However, neither the diagram nor the instructions that accompany it make any mention of the fact that there are 2 wires, rather than just 1 wire, that go to the ignition terminal on the old regulator. I spliced all 3 of the old regulator wires together along with the center wire from the new regulator plug, and I really need to know if that is correct before checking anything else.  

I always sand rusty sheet metal to bare shiny steel and coat it with dielectric grease on any contact ground point. (I have a 70 with a ECU type ignition harness so I'm not much good on the retrograde your doing.)

I use a powered wire wheel and go to the bare metal. I don't bother with grease, though it doesn't hurt anything. Any grease will do; its only function here being to provide a moisture and air barrier. Dielectric grease is relevant if there are multiple circuits that the grease is covering simultaneously; a conductive grease could cause a short in such a case; while dielectric grease (being non-conductive) will not.

When ring terminals are clamped tightly against the sheet metal with a nut, little-to-no air can get between the ring terminal and the bare sheet metal, making grease (or other forms of sealants) not particularly necessary. For this same reason, you don't need to seal a proper crimp (such as crimping a ring terminal to a wire) with anything, because a proper crimp is tight enough to be air-tight.

[nascarxx29]

 Your 69 car already had the green field wire. your just changing the type of connector plug to 70- up at that point. Changing to 2 field so now your adding the new alt blue field wire to the double blue wires that went on old regulator  on this link bottom of the page they show the 2 systems side by side
http://www.allpar.com/history/mopar/electrical.html
20. Flat-pack style electronic regulator is cheap and reliable. Virtually a must! To use it, you need any alternator with two field terminals, and the connector itself which is an easy junkyard score, or can still be had new as of 1999. Simply splice the connector, wire-color for wire-color, to the existing (old) regulator pigtails. Then simply splice in one more blue wire which you then run over to the second alternator field terminal. (If you've been using a later 2-field-terminal  alternator with a pre-'70 regulator, the second terminal would have been grounded through a short jumper wire - remove the jumper, naturally.) That's all there is to it! And you waited 25 years?

20. Flat-pack style electronic regulator is cheap and reliable. Virtually a must! To use it, you need any alternator with two field terminals, and the connector itself which is an easy junkyard score, or can still be had new as of 1999. Simply splice the connector, wire-color for wire-color, to the existing (old) regulator pigtails. Then simply splice in one more blue wire which you then run over to the second alternator field terminal. (If you've been using a later 2-field-terminal  alternator with a pre-'70 regulator, the second terminal would have been grounded through a short jumper wire - remove the jumper, naturally.) That's all there is to it! And you waited 25 years?

21. Charging-system schematic illustrates the simple differences between the old and new-style regulator wiring. Okay, you're scared of electric stuff. But this is s-o-o-o simple, Vern.

[tan top]

 , provinding  you harness is original OEM & not been altered in some way , should be like this  for a duel field alternator with 70 & later voltage regulator !!     
 i know the alternator field wires no matter which one go on what ,

[MaximRecoil]

Your 69 car already had the green field wire. your just changing the type of connector plug to 70- up at that point. Changing to 2 field so now your adding the new alt blue field wire to the double blue wires that went on old regulator  on this link bottom of the page they show the 2 systems side by side
http://www.allpar.com/history/mopar/electrical.html
20. Flat-pack style electronic regulator is cheap and reliable. Virtually a must! To use it, you need any alternator with two field terminals, and the connector itself which is an easy junkyard score, or can still be had new as of 1999. Simply splice the connector, wire-color for wire-color, to the existing (old) regulator pigtails. Then simply splice in one more blue wire which you then run over to the second alternator field terminal. (If you've been using a later 2-field-terminal  alternator with a pre-'70 regulator, the second terminal would have been grounded through a short jumper wire - remove the jumper, naturally.) That's all there is to it! And you waited 25 years?

20. Flat-pack style electronic regulator is cheap and reliable. Virtually a must! To use it, you need any alternator with two field terminals, and the connector itself which is an easy junkyard score, or can still be had new as of 1999. Simply splice the connector, wire-color for wire-color, to the existing (old) regulator pigtails. Then simply splice in one more blue wire which you then run over to the second alternator field terminal. (If you've been using a later 2-field-terminal  alternator with a pre-'70 regulator, the second terminal would have been grounded through a short jumper wire - remove the jumper, naturally.) That's all there is to it! And you waited 25 years?

21. Charging-system schematic illustrates the simple differences between the old and new-style regulator wiring. Okay, you're scared of electric stuff. But this is s-o-o-o simple, Vern.

Those instructions from E-berg don't say anything about the extra wire in the original harness either. As I've mentioned about 4 or 5 times before, there were 2 wires going to the ignition terminal of the old regulator (see the picture I posted earlier with the big yellow circle around the two wires that were factory-crimped into a quick-disconnect terminal that plugged onto the old regulator).

Also, he says, "Simply splice the connector, wire-color for wire-color, to the existing (old) regulator pigtails." That doesn't make sense, given that the new plug has a blue and a green wire (2 wires total) and the "existing (old) regulator pigtails" have a green wire, a black wire, and a black wire with a white stripe (3 wires total). So not only is a "wire-color for wire-color" splice not possible, but there is a wire count mismatch as well (2 wires on the new plug vs. 3 wires that originally plugged into the old regulator).

Also, his instructions don't seem to match up with his diagram, nor does he specify which of the two alternator field terminals "second alternator field terminal" refers to.

[tan top]

the two 2 wires are on all   !! well at least 68 & 69 cars  !!   if you un wrap the factory harness you will find one of them blue wires goes to the ballast resistor , just copy the altered picture i have posted

[MaximRecoil]

the two 2 wires are on all   !! well at least 68 & 69 cars  !!   if you un wrap the factory harness you will find one of them blue wires goes to the ballast resistor , just copy the altered picture i have posted

Your altered picture looks like it leaves one of the two ignition wires from the old regulator just hanging; not connected to anything (unless you mean that they should both be spliced into the blue wire from the new plug). Your altered picture also seems to indicate that the diagram that I originally followed ...



... is incorrect. Is that the case?

[nascarxx29]

As said above theres gonna be a double blue wires previously used on the old type regulator that used a pushed on connector.
The newly to be added field wire connects there to alternator field making 3 blue wires total
The green field wire is already there in the harness from alt to regulator your just changing to a different connector a dual terminal push on type connector for the flat type regulator .Previous regulator green field wire used a screw on connection terminal .

You should only have used the wires that went to the old regulator and addded the new blue to the old double blue wire connection
.The ballast resistor to the left on passenger side of firewall also has a single blue and brown and blue double wire.You dont mess with those wires


Hope this helps

[tan top]

the two 2 wires are on all   !! well at least 68 & 69 cars  !!   if you un wrap the factory harness you will find one of them blue wires goes to the ballast resistor , just copy the altered picture i have posted

Your altered picture looks like it leaves one of the two ignition wires from the old regulator just hanging; not connected to anything (unless you mean that they should both be spliced into the blue wire from the new plug). Your altered picture also seems to indicate that the diagram that I originally followed ...



... is incorrect. Is that the case?

sorry i'm confussed ?? hanging where  ??

green wire from new regulator goes to old green field wire harness
blue wire from new regulator goes to the two double  ignition wires on the original harness that were pluged into the original voltage regulator , then you need to splice another wire to all these blue ones & run it to the second field terminal on the alternator

As said above theres gonna be a double blue wires previously used on the old type regulator that used a pushed on connector.
The newly to be added field wire connects there to alternator field making 3 blue wires total
The green field wire is already there in the harness from alt to regulator your just changing to a different connector a dual terminal push on type connector for the flat type regulator .Previous regulator green field wire used a screw on connection terminal .

You should only have used the wires that went to the old regulator and addded the new blue to the old double blue wire connection
.The ballast resistor to the left on passenger side of firewall also has a single blue and brown and blue double wire.You dont mess with those wires


Hope this helps

[MaximRecoil]

As said above theres gonna be a double blue wires previously used on the old type regulator that used a pushed on connector.

They were not double blue wires on my car. One was black and the other was black with a white stripe:



Here is a more complete illustration of my current wiring scheme:

[MaximRecoil]

green wire from new regulator goes to old green field wire harness
blue wire from new regulator goes to the two double  ignition wires on the original harness that were pluged into the original voltage regulator , then you need to splice another wire to all these blue ones & run it to the second field terminal on the alternator

That sounds like how I already have it, assuming "second field terminal" means the terminal closest to the output stud on the alternator. See the more complete illustration that I just posted.

[tan top]

As said above theres gonna be a double blue wires previously used on the old type regulator that used a pushed on connector.

They were not double blue wires on my car. One was black and the other was black with a white stripe:



Here is a more complete illustration of my current wiring scheme:

they are two blue wires ! one dark & one with a white stripe , your prolly seeing black because with age & heat cycles the pigment has changed 

take a look at these two altered pictures ! , this is what you need to do

[MaximRecoil]

they are two blue wires ! one dark & one with a white stripe , your prolly seeing black because with age & heat cycles the pigment has changed  

take a look at these two altered pictures ! , this is what you need to do

In other words, you think I should switch the two field wires around at the alternator, because that is all your two pictures are actually indicating when compared to my illustration.

The alternator field terminal closest to the output stud is the positive field, and the other is the negative field, like so:



Your altered images indicate that the center (blue) wire of the new plug, along with the double blue ignition wires (which now look black), should run to the negative field terminal of the alternator; and the outer (green) wire of the new plug should run to the positive field of the alternator.

Both E-berg's diagram and the diagram I followed in the first place (which I've posted several times already in this thread) disagree with you. If you look at the diagram I posted in the OP (and several other posts), you will see that the center blue wire of the new plug ends up at the positive field terminal of the alternator (not the negative field terminal like in your altered images). If you look at E-berg's diagram ...



... you will see the same thing (i.e., the center blue wire of the new plug ends up at the field terminal on the alternator closest to the output stud, which is positive).

[tan top]

they are two blue wires ! one dark & one with a white stripe , your prolly seeing black because with age & heat cycles the pigment has changed  

take a look at these two altered pictures ! , this is what you need to do

In other words, you think I should switch the two field wires around at the alternator, because that is all your two pictures are actually indicating when compared to my illustration.

The alternator field terminal closest to the output stud is the positive field, and the other is the negative field, like so:



Your altered images indicate that the center (blue) wire of the new plug, along with the double blue ignition wires (which now look black), should run to the negative field terminal of the alternator; and the outer (green) wire of the new plug should run to the positive field of the alternator.

Both E-berg's diagram and the diagram I followed in the first place (which I've posted several times already in this thread) disagree with you. If you look at the diagram I posted in the OP (and several other posts), you will see that the center blue wire of the new plug ends up at the positive field terminal of the alternator (not the negative field terminal like in your altered images). If you look at E-berg's diagram ...



... you will see the same thing (i.e., the center blue wire of the new plug ends up at the field terminal on the alternator closest to the output stud, which is positive).

the blue or  green field conections  on the back of tha alternator !  does  not   matter which way round they go    , but i always put them like diagram !
but yes in answer to your question , you need to swap the conections around to the way i have altered your picture ! make sure all the splices are good , crimping is not really ideal , need to solder the splices really  

the way i have done the diagram is  the electricronic regulator  last picture you posted

[MaximRecoil]

the blue or  green field conections  on the back of tha alternator !  does  not   matter which way round they go    , but i always put them like diagram !

but yes in answer to your question , you need to swap the conections around to the way i have altered your picture !

Your altered pictures are not like the diagram; they are opposite of the diagram. Both diagrams I have posted show the center blue wire of the plug going to the positive field terminal on the alternator; which is how I have it wired on my car. Your altered pictures show the center blue wire of the plug going to the negative field terminal on the alternator.

make sure all the splices are good , crimping is not really ideal , need to solder the splices really  

Solder is far from ideal for wiring in a car environment. Solder does not flex particularly well, and given enough vibrations, it can crack/break. Crimping on the other hand, is ideal, which is why the factory that built the car crimped all the connections in the first place, rather than soldering them. Look at the bulkhead connectors sometime; there are nearly 50 factory crimps just there alone, to say nothing of the rest of the harnesses.

A proper crimp is stronger than the wire itself; meaning, you can not pull the crimped connector off without breaking the wire. A proper crimp is also airtight, which prevents corrosion. Plus, crimps are far more suitable for flexing than solder is. Solder is ideal for plumbing, attaching components to PCBs, and other applications not subject to much movement like wiring (especially in a vehicle) is.

In any event, I bypassed the alternator gauge today by attaching both wires to the same post on the back, and that got rid of the rapid fluctuations in the voltage readings, but it is only showing about 12.5 - 12.7 volts at the battery when the engine is idling. It is also only showing about 12.5 volts at the alternator. And just for the heck of it, I did try it with the 2 field wires at the alternator switched around, with no change in results.

Is this a system that only charges when it needs to, i.e., when there is a draw on the system (such as headlights)? I don't have my headlights wired up yet, so I haven't been able to test the voltage with the headlights on.

[nascarxx29]

The double blue connection wires usually is blue with white tracer and a dark blue.Hopefully you got it straightened out and working

[MaximRecoil]

The double blue connection wires usually is blue with white tracer and a dark blue.

Yes; they look black in my car, but I can see that they were probably once dark blue.

Hopefully you got it straightened out and working

Well it seems that I've had the wiring correct all along, but I'm still only showing 12.5 - 12.7 volts at the battery, and about 12.5 at the alternator. Those voltage readings were relatively steady after I bypassed the car's alternator gauge (prior to doing that, the voltage fluctuated rapidly between mid 12s and low 13s).

Also, the battery that is in there now is not so great (it won't hold a charge for very long). Could that be the problem?

[nascarxx29]

A good battery will help

[tan top]

the blue or  green field conections  on the back of tha alternator !  does  not   matter which way round they go    , but i always put them like diagram !

but yes in answer to your question , you need to swap the conections around to the way i have altered your picture !

Your altered pictures are not like the diagram; they are opposite of the diagram. Both diagrams I have posted show the center blue wire of the plug going to the positive field terminal on the alternator; which is how I have it wired on my car. Your altered pictures show the center blue wire of the plug going to the negative field terminal on the alternator.

make sure all the splices are good , crimping is not really ideal , need to solder the splices really  

Solder is far from ideal for wiring in a car environment. Solder does not flex particularly well, and given enough vibrations, it can crack/break. Crimping on the other hand, is ideal, which is why the factory that built the car crimped all the connections in the first place, rather than soldering them. Look at the bulkhead connectors sometime; there are nearly 50 factory crimps just there alone, to say nothing of the rest of the harnesses.

A proper crimp is stronger than the wire itself; meaning, you can not pull the crimped connector off without breaking the wire. A proper crimp is also airtight, which prevents corrosion. Plus, crimps are far more suitable for flexing than solder is. Solder is ideal for plumbing, attaching components to PCBs, and other applications not subject to much movement like wiring (especially in a vehicle) is.

In any event, I bypassed the alternator gauge today by attaching both wires to the same post on the back, and that got rid of the rapid fluctuations in the voltage readings, but it is only showing about 12.5 - 12.7 volts at the battery when the engine is idling. It is also only showing about 12.5 volts at the alternator. And just for the heck of it, I did try it with the 2 field wires at the alternator switched around, with no change in results.

Is this a system that only charges when it needs to, i.e., when there is a draw on the system (such as headlights)? I don't have my headlights wired up yet, so I haven't been able to test the voltage with the headlights on.

 

sounds like you got it fixed ?  & no  need for my help after all , thanks ! i think ,for letting me try & help you though! !  

good you got it sorted   

[MaximRecoil]

 

sounds like you got it fixed ?  & no  need for my help after all , thanks ! i think ,for letting me try & help you though! !  

good you got it sorted   

Fixed? No. I haven't changed anything since I started this thread other than bypassing the alternator gauge. As far as I know I should be getting a relatively steady voltage reading in the high 13s to low 14s at the battery while the engine is running, but I'm only getting mid-to-high 12s.

Here's some questions from this thread that I'm still wondering about:

1. I've heard that the car's alternator gauge is a critical part of the charging circuit, so if something is screwy with that, it won't charge properly. I was thinking about adding a jumper wire across the two terminals of the gauge to eliminate that potential problem (any thoughts on this?).

2. Are there any other parts of the charging circuit I should test?

3. Is this a system that only charges when it needs to, i.e., when there is a draw on the system (such as headlights)?

[b5blue]

A nothing less that excellent battery is mandatory for these old factory systems to have any hope. (Due to weak idle output.)

[nascarxx29]

You need to have a good battery stationary voltage should read 12 or 12.5 volts.With out the car running.Running should be 13.5 or then some.Mopars discharge at low speed to due pulley speed inherit problem.And there many modifications to improve on the mopar charging system. From GM or Powermaster 1 wire alternator or a Nippo Denso Japanese unit

http://www.dodgecharger.com/forum/index.php/topic,64454.msg721348/topicseen.html#msg721348

[tan top]

A nothing less that excellent battery is mandatory for these old factory systems to have any hope. (Due to weak idle output.)

You need to have a good battery stationary voltage should read 12 or 12.5 volts.With out the car running.Running should be 13.5 or then some.Mopars discharge at low speed to due pulley speed inherit problem.And there many modifications to improve on the mopar charging system. From GM or Powermaster 1 wire alternator or a Nippo Denso Japanese unit

http://www.dodgecharger.com/forum/index.php/topic,64454.msg721348/topicseen.html#msg721348

1 -- as far as i know  the amp gauge only really gives problems when the connections become loose & or the insulation brakes down & causes a short ?? then big problems !
http://www.madelectrical.com/electrical-tech.shtml
i would bolt them togeather & insulate !  completely by pass the amp gauge ,  infact thats what i have done my self ,( & converted factory amp to a volt gauge ) but my own take on the mad amp meter by pass , & more or less  completely redesigned the whole charging circuit / power supply  , ( got a bit carried away really adding blade fuses & stuff to protect circuts , & prolly no need of that many , but while i was redoing  stuff , might as well put them in , just my preference ) but still using the  factory duel filed alternator !

using a jumper wire between the two terminals on the rear of the amp gauge ,  would work , but would be worried about more stuff being bolted & the already inadequate terminal insulation through the grounded metal gauge cluster body !   !!

like was mentioned the mopar idle charging , at least with the oem alternators  is not good !!  , to make sure its charging  properly  i would increase the revs to 1200ish rpm while checking  just to eliminate low  oem mopar charging at  idle .

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2 -- would check the  firewall block connector  , the middle one carries the battery / alternator charging power , make sure they are free from corrosion etc , big mopar problem especially on cars that have been sitting for any length of time , would be a good idea to check the lot while your at it , & any broken or frayed wires ! check & clean starter relay conections too

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3

yes  sort of ,   battery volts should be at least 12.5 -12.8ish + - , when engine not running
with motor idling with no electrical load about 13.5  - 14.8 + - even as high as 15 , but anything over you have a problem , when using   high load electrical stuff, headlights , blower fan motor !  etc etc if you wire up a volt meter when the motor is running you will see a momentary drop in voltage , but then if every thing working ok , it will return to about  idling with no electrical load 13.5 .14.8 ,
although like i mentioned , mopar charging at idle is not the best , so would increase revs to what i have previously mentioned , to check!

lastly , if your charging system is working correctaly , & your battery is partialy discharged ! when you start the motor , the amp & or volt meter will prolly read as high as 15.5 volts  or 20ish + amps while the alternator is charging the battery up  ,  the gauge should return to just to the plus side on the amp gauge & 13.5 -14.8 on a volt gauge/meter after a short while , minute or two

below
another picture how the 70 & up electronic voltage regulator should be hooked up

[elacruze]

Test for AC voltage across the alternator stud and case, maybe you lost one of the diodes. If you lose a diode you lose 1/3 of the capacity, and either lose the circuit completely or it goes AC and becomes neutral to the charging process. You can test the diodes individually but you may have to take the case apart. You should be able to find an auto parts with a proper alternator test stand somewhere nearby.

[MaximRecoil]

Test for AC voltage across the alternator stud and case, maybe you lost one of the diodes. If you lose a diode you lose 1/3 of the capacity, and either lose the circuit completely or it goes AC and becomes neutral to the charging process. You can test the diodes individually but you may have to take the case apart. You should be able to find an auto parts with a proper alternator test stand somewhere nearby.

How much AC voltage would be correct?

So does the case of the alternator need to be grounded? I'm sure it is already grounded because it is installed using clean factory brackets, but if the ground of the alternator case is critical, I could add a dedicated ground wire to it to be sure.

[elacruze]

Test for AC voltage across the alternator stud and case, maybe you lost one of the diodes. If you lose a diode you lose 1/3 of the capacity, and either lose the circuit completely or it goes AC and becomes neutral to the charging process. You can test the diodes individually but you may have to take the case apart. You should be able to find an auto parts with a proper alternator test stand somewhere nearby.

How much AC voltage would be correct?

So does the case of the alternator need to be grounded? I'm sure it is already grounded because it is installed using clean factory brackets, but if the ground of the alternator case is critical, I could add a dedicated ground wire to it to be sure.

Theoretically, there should be Zero AC voltage. Typically in my system I find .3-.5 volts AC. I have a dual-field squareback 78 amp unit from a '96 Durango, but there is little difference all the way back to '74 or so. Even the older single-field alts should have no AC voltage.

Case ground is critical on single field alts since the circuit is completed through the case, but not so important on dual field since the regulator controls the ground circuit through the fields. I always insure a secure ground in any case, just to be certain nothing can be ground looped. (ground loop is a difference in electrical potential at different grounding points)

[MaximRecoil]

Okay, so if I get significant AC voltage across the alternator stud and case, that means I've got a bad diode and the alternator is doing nothing to charge the battery?

I believe the system is charging somewhat. I show ~12.5 VDC across the alternator stud and ground, and the battery shows a relatively steady 12.5 - 12.7 VDC while idling (revving the engine doesn't change the voltage). The reason I believe the system is charging somewhat is because before I did the electronic regulator conversion, I know for a fact it wasn't charging, and the battery voltage would be at around 12.5 VDC before starting, but would drop to around 10.5 volts within a minute or two of idling. But the way it is now, it just stays at 12.5 - 12.7 VDC even if I let it idle for 20 minutes. If it wasn't charging at all, the battery voltage would drop quite low after 20 minutes of idling, rather than stay the same.

The first thing I'm going to try is to swap in a different regulator and/or alternator to see what effect that has (there are lots of Mopar regulators and alternators in the junkyard behind the place where I'm working on the car).

[MaximRecoil]

I switched the alternator with another one this morning, and no change. Then I was about to look for another regulator to try when my mechanic friend walked over. He unplugged the regulator as the car was idling and wanted me to check the voltage. It dropped to 9 someodd volts when he did that (bad battery and all), down from about 12.5 VDC when the regulator was plugged in. Then he jumped something on the regulator and/or plug with a screwdriver, and wanted to know what the voltage was now. It jumped to 16 or 17 VDC at the battery when he did that. He said, "It's the regulator. Grab one off that Dodge van over there." He was right. When I hooked up the other regulator, I got 14 VDC at low idle at the battery, and 14.4 VDC at high idle.

[b5blue]

 

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