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Battery Charging System - Wiring Diagram Questions
Very long... I hope someone has the patience to go through this and provide answers to these questions. It will help me understand a wiring diagram I have.
First of all, I hate working on cars. But I'm helping someone debug a charging problem. I have experience with electronics (not automobiles however) and am having a bit of difficulty deciphering a wiring diagram. Many of the details about which contacts are thrown, connecting which power to which points, seems to be left to those who already understand how car electronics work.
Anyway, to help me understand, I'd like to show the diagram and ask some specific questions. The automobile is a 1980 Dodge Ramcharger. I have a wiring diagram for this year model.
The problem: The truck will start and run, but will not charge the battery. I have checked the battery and it is showing low voltage AND the input and output to the Voltage Regulator is (11VDC using a DMM). I'm not sure what the value should be but I would expect it to be between 12 and 14, if the battery is not charged.
The Alternator, VR and Starting Relay have all been replaced but the battery still won't charge. I'm thinking there is a connection problem that's preventing the VR from sensing the battery level and therefore not providing the necessary feedback to cause the alternator to generate sufficient current to charge the battery.
I have also bypassed the Amp Meter and that is not the source of the problem. Besides if it were open, the truck wouldn't start and it does. However I checked it anyway. Also, when running the amp meter doesn't show any reading, which also makes me think it's a connection problem; just not the main connection, since the truck will start and run, with the amp meter in, but won't start with the amp meter circuit open.
All this this leads me to believe that the voltage regulator isn't monitoring the battery voltage.
Some Questions (Refer to diagram above):
First question. Does RED always mean 12VDC and BLK always mean GND on these wiring diagrams? Or are there exceptions?
Battery Sensing Path: The main problem I'm having is understanding the path from 12VDC, to the Voltage Regulator, so that the VR can sense battery voltage. One path I see might be: From the 12V, to the Starter Relay block, out on the DK GRN wire, to the Fuse Link, to the AMP meter, to the Fuse Link, to the RED wire on the Ignition Switch, and back out on the DK BLU wire, to the Alternator and VR. But I don't know if that is the correct path. If that is the correct path, that would mean that DK BLU would be connected to RED on the ignition switch, when turned on. Is that the correct path or is there a different path for VR to sense Battery level?
Charging path: It's also not clear what the charging path is. But it seems likely it would be the reverse of what was stated in 1. This also makes sense since it goes through the AMP meter which can measure current in both directions. Is that the charging path, or is there another path? We have already bypassed the AMP Meter, so we know it's not an open meter that is preventing the battery from charging. Also, the meter doesn't move, which makes me think bad connection.
With the truck not running but with the ignition switch on, should the battery voltage be seen at the RED terminal on the Voltage Regulator?
Another problem I have is understanding why the amp meter circuit has to be complete, before the starter will turn over. According to the diagram, it's not in the amp meter circuit.
On the starter relay, shown in the image above, there is a terminal block for the RED (+) connections and there are 4 other connections shown in the diagram (ORN, PNK, BRN and DK GRN/White). But it's not clear when the 12V or GND is applied to these other terminals (i.e. when energized or de-energized). Can someone define this? *** I assume PNK has 12VDC applied, when starter relay is energized and open when de-energized (ballist bypass). Correct?
I assume BRN has 12VDC applied, when starter relay is energized and open when de-energized (power to starter). Correct?
But I'm not sure about the ORN connection. Is that 12V, to the ignition switch? Or is it the 12V applied, to the starter relay coil, that actuates that relay. Or something else?
Also not sure about the DK GRN/WHT line or what it's for.
On the Ignition Switch block, there are YEL, BLU/RED, DK BLU, RED, PNK/BLU and BLK. It's not clear which has 12, GND or when they are applied. When switch is on or off? Which wires are connected, when the switch is On/Off? Normally I would assume RED is 12V and BLK is GND. But when these are connected to other points on the switch isn't clear. Can someone define this, for the diagram included above?
I'm also not sure why there are two connections to the low side of the AMP meter. One connection goes to the BLK wire on the alternator. The other wire goes to the RED wire on the ignition swich, through a Fuse link. Can someone explain why there are two connections on this side of the AMP meter (refer to diagram above)
I know... a lot of questions. But if someone has the time to sift through these and reference the diagram shown, I'd appreciate some help understanding this diagram. I'm used to schematics where relays and switches show which connections are made/broken when switches and relays are thrown.
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with the mopars, blue is always the hot wire. red is not always positive and black usually is ground. have you tried running a temporary jumper wire from the big post on the alt directly to the positive post on the batt. [for testing only]
What voltage are you getting from the Post on the alt [to ground] at fast idle?
My guess would be bad batt connections or bad alt. By the way I've got a 1980 power wagon. They're known for bad connection at the bulhead connection.
with the mopars, blue is always the hot wire. red is not always positive and black usually is ground.
have you tried running a temporary jumper wire from the big post on the alt directly to the positive post on the batt. [for testing only]
Not yet but it was something I had planned to try. Very cold right now so I'm just researching the wiring diagram.
What voltage are you getting from the Post on the alt [to ground] at fast idle?
It's about 11 volts. Seems low.
My guess would be bad batt connections or bad alt.
The alternator, voltage regulator and battery have all been replaced.
I'm thinking it might be a burned wire or bad connection coming from the ignition switch. But I'm having a difficult time tracing through the wiring diagram. I'm used to clear schematics and the wiring diagram leaves a few things out (like what contacts are made with what wires, when switches and relays are thrown).
Does the charging current run through the ignition switch? I'm wondering if it might be the DK BLU wire that is the problem (burned or bad connection).
Is this the charging path (see link below)? Kind of a bad copy of the wiring diagram.
I DO know the continuity is good between the RED wire on the alternator to the ballast (GREEN Path in diagram; tested).
I DO know the continuity is good between the ballast and the VR input (GREEN Path in diagram; tested).
And since the truck starts I know the continuity is good from the battery to the ignition switch (PURPLE path; assumed because truck starts).
That leaves only the DK BLU wire that is untested and if this is the charging path, it seems like a good likelyhood, since it's the only path not specifically tested.
If you can read this schematic, does this look like the correct charging path?
The other question I have is the purpose of the wire running from the BLK wire on the alternator, to the low side of the alternator switch. If my assumption is correct on the charging path, I don't understand the BLK wire's purpose. Please refer to the wiring diagram, for an answer to this.
What is the specific purpose of this path? It doesn't seem to be related to charging but it's connected to the alternator.
Well like I already said, I have bypassed the amp guage to rule it out as the cause.
Everything I have already tried is in my first post. My problem now is just understanding the wiring diagram. I'm 100% sure I'll figure this out, once I understand the diagram. It's just that some connections aren't shown in the diagram, so it's a little hard to follow.
First let me say my eyes may not be as good as they used to be so these wiring diagrams are not real clear on my screen.
1. Is this the charging path (see link below)? Kind of a bad copy of the wiring diagram.
The answer to this question is yes.
2. And since the truck starts I know the continuity is good from the battery to the ignition switch (PURPLE path; assumed because truck starts).
The purple path has nothing to do with the starting of the truck except the part from the battery to the starter. The starter circuit includes the top wire out of the ignition switch, yellow I think, and the red from the battery to the starter and the power to the ignition switch from the battery.
3. What is the specific purpose of this path? It doesn't seem to be related to charging but it's connected to the alternator.
Charging current never flows directly thru an ammeter. Ammeters are always connected in a parallel way to the actual charging circuit. I don't believe you can see this whole ammeter thing on your diagram as it is very vague in the connection department.
4. The other question I have is the purpose of the wire running from the BLK wire on the alternator, to the low side of the alternator switch. If my assumption is correct on the charging path, I don't understand the BLK wire's purpose. Please refer to the wiring diagram, for an answer to this.
The BLK wire from the alternator to the ammeter is part of the parallel circuit that feeds the ammeter.
If it were me I would suspect one of the fusible links if the alternator is good.
Thanks, but now I'm a little more confused. Some followups.
1) In your answer in #1, you say "yes" the path indicated is the charging path. But that path goes through the ampmeter, according to the diagram.
Then in #3 you say the charging current never goes directly through the ampmeter. This seems to contridict the answer given in #1, since that path has the ampmeter in it. Also, the ampmeter shows charge and discharge, so it seems the ampmeter should be in the charging path.
Perhaps I'm confused by what you mean. I DO understand that typically an ampmeter is just a volt meter and the voltage is developed across a shunt resistor (in the meter itself). If that's what you mean, I understand but that wouldn't then change the point of my questions or assumptions.
2) Your answer:
"The purple path has nothing to do with the starting of the truck except the part from the battery to the starter."
Yes, I understand that. The purple path is the source of +12V to the ignition switch (I believe). That path is connected to the Yellow wire, when the truck is started. So since the truck starts, all of that path is good, including the purple path. And since that path has the fusible links, they must also be good.
3) Your answer:
"If it were me I would suspect one of the fusible links if the alternator is good. "
I don't think it's a fusible links (unless there is one not shown), because if I open up the ampmeter circuit, the truck won't start. If I short around it, it does start. And those fusible links are in that path (purple path), which I know is good. The fact the truck will start only when that path is closed seems to imply the links are good.
4) I'm still confused about the specific purpose of the BLK wire going from the alternator to the meter. The meter path is all hot, implying the BLK wire is hot also. The alternator shows 4 wires connected.
LT GRN (field connection),
RED (output, I assume),
BLK wire on left, in diagram (chassis ground)
BLK wires on right, in diagram (????)
But the one on the right, in the diagram is confusing me, as to it's purpose. It must be hot, since it goes to the ampmeter also. But exactly what does it do.
5) Your answer:
"I don't believe you can see this whole ammeter thing on your diagram as it is very vague in the connection department."
Now you see why I'm confused.
NOTE: To anyone else joining in at this point. I refer to paths and colors. You need to look at the images in the links I previously provided and the descriptions or you won't be able to follow anything after that point.
6) I know I'll eventually find the problem. It would just be quicker if I understood the exact (and complete) charging current path from alternator to battery. Along with this I also understand that the VR has to sense actual battery voltage and that is the wire from RED on VR to RED on Alternator but that is already checked good.
The VR and Alternator have already been replaced. So, I'm thinking connection in the charging path, that doesn't affect anything but charging.
I have made some statements that are based on what I know to be true but are not shown on your diagram. If you tried to run all current thru an ammeter the wiring in the ammeter would have to be massive and that is why you run it parallel to the full load. I also said that your wiring diagram is very vague and does not show this well. Look up other wiring diagrams and you will understand. Most of your confusion is due to a poor quality wiring diagram. ie. Where is the fuse in the line to the wiper switch where we all know one is used? I would s**t can that diagram and head to the local library and get a copy of a decent diagram. I know that there are people on this forum that have access to ALLDATA and might be able to get you a better diagram.