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Discussion Starter · #1 ·
There are so many help files on here that I can usually find what I'm looking for, but not today.  My thanks to the many contributors. 

I'm running a 77 with stock electric.  I developed low voltage issues after a recent alternator change.  In spite of the fact that I had no sign of shorted circuits or undue parasitic loss, the popular consensus was to perform the infamous amp gauge bypass.  It was a simple and popular procedure, so I figured I had nothing to loose.  Unfortunately, it didn't help and now I have multiple electrical issues (shorts, parasitic drain, etc).  I figure, I must have moved some things around under the dash.  I'm testing all the wiring one by one with a multimeter.

As it turns out, NAPA gave me the wrong alternator.  So the low voltage issue should be resolved.  Just the same, I'm working on a charging circuit upgrade.   

And finally to a question...

I dumped the 10 gauge output wire from the alternator and replaced it with 6 gauge.  Maybe it's overkill, but when I finish working out the bugs I may move to a HO alternator.  I crimped and soldered the connectors, and cleaned all the connecting surfaces.  I fully expected to get a "0.00" volt reading when testing the charging wire from alternator to starter relay, but I didn't.  I'm getting 0.05v.  What do you think?  Is that  ... "normal"?

 

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All circuits contain atleast some resistance, it is inherent. .05 is a GOOD reading. Way better than "normal" for a 30 year old truck. Under .3 for + side and .2 for negative side is "good enuf for that guy".

Measure directly off battery + post instead of relay, keep the other one on alternator like you had it, reading may or may not increase.

Turn on all major loads that you can, the more the merrier. Bring rpms up to atleast 2000-2500 so the alternator is capable of putting out more current. (more current tends to equal higher reading)

Test with engine bay hot.

If highbeams/blower motor is not enough current for your testing, an autozone "technician" ::) can wheel out the alt load tester. They can hook the clamp up to alt charge cable (arrow pointing towards battery) and hook up the battery and slowly increase current load on their dial until your reading rises or output ceases to rise. If reading is still very low like that, and alternator has sufficient output, you have an excellent circuit. (remember to ensure heatsoaked engine bay and enough rpms)
The test is to be shut off at first notice of either test failing. (output amps or voltage drop across cable) continued testing beyond specs (high v-drop reading or current draw beyond alt capacity) may result in engine fire or damaged components.

Releasing the test knob too rapidly will also create an induction spike that may fry the very few sensitive electrical components you have. Depending on cable length and current draw, the spike will possibly be well over 100volts but for such a brief milliseconds that a multimeter will likely never display it. It specifically targets sensitive light bulbs and transistors. Only important transistors you have are the ign module and regulator, but they are quite important. The battery can absorb a good spike but it's best to not tempt fate.

If it passes under heatsoaked conditions (similar to hot restart/idle traffic) it will certainly pass in all cooler conditions with less than full load.

http://ramchargercentral.com/vehicle-help/where-my-electricity-went/
http://ramchargercentral.com/vehicle-help/86-rc-voltage-fluctuation/
http://ramchargercentral.com/vehicle-help/voltage-regulator-charging-issues-%28fixed!!!!!!!!!!%29/
http://ramchargercentral.com/vehicle-help/e-fan-conversion/msg1555681/#msg1555681

In previous post where I had said "I believe 6ga is stock" I should have clarified stock for the late model high output nippondenso alternators.
 

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Discussion Starter · #3 ·
s ǝoɾ said:
Measure directly off battery + post instead of relay, keep the other one on alternator like you had it, reading may or may not increase.
I'm getting .07 alternator output to positive battery post

alt case to negative post is 0.00/0.01

s ǝoɾ said:
Bring rpms up to at least 2000-2500 so the alternator is capable of putting out more current. (more current tends to equal higher reading)

Test with engine bay hot.
Same results, but I can't remember if I ran that test with everything on. I'll play with it more later.
 

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Copper Top said:
I'm getting .07 alternator output to positive battery post

alt case to negative post is 0.00/0.01
Same results, but I can't remember if I ran that test with everything on. I'll play with it more later.
If you can maintain those specs under a load, you are doing awesome! {cool}

If I am doing my math correctly, (could be off) I believe this means are are losing approx 1/2% through the cables/connections, or in other words 99.5% is making it to the battery. You can not have 100% something WILL get lost along the way. Of course, without any lights or blowers on, the only thing your alternator is putting out is a few amps to charge the battery (depending on state of charge) and a few amps for the ignition module/alternator field/ignition coil.

As the load is increased either with more vehicle equipment or a carbon pile load tester, you will likely experience more dropped or lost as heat. You will also find the number changes based on temperature, since temperature affects conductivity. That is why I recommend a worst case scenario hot full load.

I plan to purchase a used intake manifold heater off a cummins. Dual elements, each between 90-105amp current draw. A single one of those can easily simulate a full load for alt testing, and connecting both heaters can simulate the cranking draw of most gasoline engines. (the starter itself can be used as a good load tester for the starter cable if you disable ignition coil and know your starter works properly)

Feel free to check various other grounds to ground areas. Examples include core support to batt neg (headlights on) alt regulator case to batt neg, engine block to batt neg, or any other area while devices are powered and drawing current. (test doesn't work if everything is turned off)
 

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Discussion Starter · #5 ·
Engine Off Battery
    Cold (before test) 12.75    Hot (After Test) 13.00
Battery Case
    0.00
Engine Running Battery (readings showed no change on any tests 2000 rpm and beyond)
    Cold (idle) 15.00 (load) 14.75
    Cold (rpm) 15.15 (load) 15.22
    Hot (idle) 14.95/14.97 (load) 13.55/13.85 (fluctuates between readings)
    Hot (rpm) 14.99 (load) 15.15 (numbers remain stable)
Alternator Stud to Positive Post
    Cold (idle) no load .07, lights only .09, wipers only .08, Fan only .11, All .15
    Hot (idle) – All .12/.15 (reading fluctuates)
    Hot (rpm) – All .17/.18 (reading fluctuates)
Alternator stud to Negative Post
    Hot (idle) 15.15 (load) 13.75
    Hot (rpm) 15.15 (load) 15.5
Negative Post to Ground
    Alternator Case (idle) 0.00/0.01 (load) 0.03/0.04
    Alternator Case (rpm) 0.00 (load) 0.04
    VR (idle & rpm) 0.00 (load) 0.01
    Radiator (idle & rpm) 0.00 (load) 0.01
    Block (idle & rpm) 0.00 (load) 0.01
    Frame (idle & rpm) 0.00 (load) 0.01

The voltage seems generally high.  I gradually loose voltage between posts at the battery, under full load at idle; it gradually increases at idle without a load.  I'm stumped.  Thanks for the help.
 

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Am I missing something?  Your initial post says you had a low voltage problem, but your last post says and indicates a high voltage problem.  Your last post tells me you have a bad v. regulator.  Don't care if it's new out of the box, I've come across several in person and here that were bad that way.  Try again with another one, preferably different brand and different store.
 

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Discussion Starter · #8 ·
ToxicDoc said:
Am I missing something?
Maybe.
Here is what my first post actually said.
Copper Top said:
… As it turns out, NAPA gave me the wrong alternator. So the low voltage issue should be resolved. Just the same, I'm working on a charging circuit upgrade.
I thought the history was important; maybe it was too much and not enough. Here is some more. I bought the truck. It had low voltage problems. I could find no significant electrical issues (shorts, burnt wires, etc). I replaced the alternator and voltage regulator (it was old and noisy; I figured it needed replaced anyway). It still had low voltage problems. I performed the bypass. I developed many electrical problems. I've been tracking them down one by one; mostly adding and cleaning grounds, cleaning all contacts, unwrapping all the wiring to visually inspect and test for voltage and continuity. In the process, I identified that I brought home the wrong alternator. At this point, it's much better than what I started with, but it still has problems.
ToxicDoc said:
Your initial post says you had a low voltage problem, but your last post says and indicates a high voltage problem.
At the moment, I'd say it's both. I seem to be losing voltage at idle under a full load, and I have too much when I'm not at idle. I don't know how to interpret it. That's why I'm asking for help. I easily have 100 hours in this problem. I've learned a lot about troubleshooting, but I've reached an impasse. I'm sure I can benefit from all the wisdom on here.
ToxicDoc said:
Your last post tells me you have a bad v. regulator. Don't care if it's new out of the box, I've come across several in person and here that were bad that way. Try again with another one, preferably different brand and different store.
Well. That seems logical. But, I'm already on my second one. And the one I have, I took back to be tested and it came out fine. Any other thoughts before I buy another one? Any suggestions on brand? I haven't been to impressed with NAPA as of late. Any favorites on part stores?

Thanks again.
I really appreciate the help.
 

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Discussion Starter · #9 ·
s ǝoɾ said:
What color are the 2 wires on your regulator?
Red and Yellow. Yellow goes to the "center" of the VR, red goes to the ballast. Just before the ballast is a group welded splice of red wires. 2 go to the top ballast plug, 1 to the ECU (brain), 1 with a 6" pigtail ending in a connector that doesn't connect to anything, 1 through the bulkhead connector, and 1 back to the VR.

Is there more than one type of VR for these?

Thanks
 

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losing voltage at idle is typical with the older dodges.mine has done it for the last 18 years.i got used to it.
 

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Discussion Starter · #11 ·
offroader_dodge said:
losing voltage at idle is typical with the older dodges.mine has done it for the last 18 years.i got used to it.
When I started this escapade, it would barely blink the turn signals at an intersection when the wipers and the blower were running with the lights on. The last thing you want on a cloudy, rainy day is dim lights and fogged up windows. It's doing much better now. The meter shows it draining, but it's hardly noticable from the using end. I can live with the low end, if that's the best we can do. It's the high end I'm most concened about. The instrument cluster voltage limiter went out. I'm guessing it may have been the high voltage. I'd like to either fix it or get the "It's ok" before i spend the 40.00 for a new one.
 

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I don't have or know the wiring schematic for your vehicle, but the only other thing that comes to mind could be low voltage (ie too much resistance) in the reference wire used for the V-reg. 

The V-reg has two wires - one coming back from the alternator field (which it will ground to let the alternator put out current) and the other coming from your ignition-activated circuit (reference wire). 

If the reference voltage source is lower than the battery, the v-reg will activate the field more in order to "see" the correct voltage at the referece wire.  That is the one to check now.
 

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Discussion Starter · #13 ·
ToxicDoc said:
I don't have or know the wiring schematic for your vehicle, but the only other thing that comes to mind could be low voltage (ie too much resistance) in the reference wire used for the V-reg.
I just spent the past couple hours reading as much as I could find on the topic. It's about the only thing I haven't "tested". I did unwrap, visually inspect, and feel the VR field wires. They look like brand new.

I've run across several articles leading up to the point where "you might need to test" them and how troublesome it is, but not how to do it or what readings to look for. Maybe I missed it.

A continuity test didn't prove anything. Obviously, something is getting through.

I suppose I could replace it with a temporary jumper and see if that resolves the issues. Or, if I do choose to pierce the wire, I'm guessing the red wire from the ballast would read 12v and the yellow wire from the VR would be a variable voltage based on demand? If I remember right, the VR to alt wire is a controlled ground. Is that right?

I'll chip at it some more tomorrow evening.
 

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Couldn't tell you about the colors, but the circuit goes like this:

"12" volt switched wire to V-reg.  then possibly a feeder wire off of that (or a separate, independent wire) goes to the alternator brush.  The current goes in there and out the other brush terminal.  From there, that other wire goes back to the V-reg, where it gets grounded (to create charge at the alternator) until the v-reg sees the voltage it likes.

The return wire from the alternator isn't variable.  It is "12" volts and gets ground control by the v-reg.

You can jumper current, but not sure how you would physically do that without damaging the molded plug.  I would simply remove the plug and check what the voltage there is compared to battery voltage.  If it's lower, you have a resistance problem in the circuit.  You can accept a little lower if the running voltage isn't too high, but we've established it is at the moment.
 

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Discussion Starter · #16 ·
s ǝoɾ said:
Measure red wire from alt end to bat +. This is your reference AND + field wire, it is very suspicious. It will likely read over my prescribed .300, at which point it has failed.
Yellow alternator connection to battery
(cold) 12.5 (warm) 6.0
Red alternator connection to Battery
(cold) .84 (warm) .60
Red alternator connection to red wire weld assembly at ballast.
(cold) .20 (warm) .10
Battery to red wire weld assembly at ballast.
(warm) .47

If I'm reading this right, that means I have resistance in the power from the ignition switch to where it joins the red wire assembly near the ballast. I'm guessing this is where it gets fun. These circuits must be harder to check when it's running. Some of them, I can check through the back of the connector. The rest, I guess I start shoving needles in the wires? Can I accomplish anything at the fuse box?

Am I drawing the right conclusion? What am I missing?
 

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You are correct.  Did you check actual voltage at the weld assembly compared to battery voltage?  I'm just curious what you are getting.

Next place I would check now is battery + to the terminal at the bulkhead connector.  This will help narrow down if the resistance is under the hood or somewhere within the cab (ie ignition switch/connectors).
 

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Discussion Starter · #18 ·
ToxicDoc said:
You are correct. Did you check actual voltage at the weld assembly compared to battery voltage? I'm just curious what you are getting.
When the battery was 15.00 the Weld was 14.6

ToxicDoc said:
Next place I would check now is battery + to the terminal at the bulkhead connector. This will help narrow down if the resistance is under the hood or somewhere within the cab (ie ignition switch/connectors).
15.3 going in, 14.6 coming out. I'd say that makes it in the cab.

I started probing wires at the connectors under the dash. The only thing I have found noteworthy so far is a pink wire coming from the ignition switch (.46). It goes out to the ballast and then to the coil. I don't see how that would be related to the charging issue.

I need to make some longer wires so probing will be a little easier.
 

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also,you can never be grounded enough.i like to overkill my grounding circuits.Especially cab to engine.
 

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Discussion Starter · #20 ·
offroader_dodge said:
also,you can never be grounded enough.i like to overkill my grounding circuits.Especially cab to engine.
I added a ground from the back of the block to one of the mounting bolts on the VR. Another from battery direct to frame. Cleaned and changed to soldered connectors at the radiator/light junction and to the front of the block. All my grounds are reading 0.00 to battery. Some of them will flash occasionally to 0.01 at 2000rpms. Firewall to dash grounds are all reading 0.00/0.01. It seems I'm grounded. I'll double check some spots under the dash to ensure I'm not loosing something from firewall to dash. I can't remember if I checked battery to dash. Maybe add another ground.
 
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