Overcharging problems

[carmart1975]

Hey it’s the stupid kid again. I have been fighting with my duster for about a year now I’ve always had problems with the voltage bouncing between 14 and 15 V at idle and in drive. It had the same problem when I had a 60 amp alternator in it and then I had stalling problems because I put an electric fan in it so I put a 95 amp in it nothing changed and it still sits a 15 V I’ve probably put about six regulators in it. I have a Mopar performance in it. It was perfect for about two weeks and this week it started bouncing again. I’ve checked all my grounds. I don’t know what to do at this point please help.

 

[Oldmanmopar]

The blue wire going to the voltage regulator is probably your issue. All the blue wires under the hood are connected together near the master cylinder in the harness.

Follow it from the ballast resister and it will lead you to a solder joint where they are all connected. I believe that may be your problem.

Somewhere you are losing power to the voltage regulator. That is the wire that controls the charging from the alternator. Fix that wire and your problems should be corrected. That would be the first place I would look.

 

[Mattax]

IMO the problems are only exaggerated by the electric fan.
The higher 'rated' alt may or may not be capable of producing more power at idle rpm.
'75 power distribution is a little different than previous years. (I've posted diagrams of that) Depending on where you tapped in higher current may be restricted. If you've also modified the battery feed, then you'll have to post a drawing for what you did so others can know what you're working with.

 

[67Dart273]

This problem is likely made worse by the added fan IF you have stock wiring. Look up this article which slantsixdan LOVES TO CRITICIZE but I post it BECAUSE it points out the why and how of the base problem. Then rather than doing what they did, repair the bulkhead terminals because you STILL NEED THEM to feed the interior, and then make up a large gauge jumper cable direct --with a fuse-- from the alternator output to the battery.

Catalog

HOW THIS PROBLEM (usually) works.

Look at the diagram in the article. ALL of the terminal points in the diagram can cause voltage drop between the battery, alternator, and back to the "run" circuit in the engine bay. The path is battery--fuse link--bulkhead connector (big RED) to ammeter--out on big BLACK--welded splice--back through the bulkhead connector and to the alternator

The DROP to the VR starts at the same place, and after the welded splice goes to ignition switch connector-- through the switch -- back out the switch connector on BLUE "run" wire--out the bulkhead connector --and into the engine bay where it branches off, feeding the ignition system, the VR, the alternator field on 70/ later, electric choke if used, and smog doo dads on later cars.

THIS DROP causes the VR to "think" the battery is low, and ramps up the alternator until the blue "under the hood" meets 14V. BUT THE BATTERY IS ON the other end of the voltage drop so it sees 15V or so, whatever the amount of the drop

HOW TO CHECK

With key in "run" but engine stopped, stab one probe of your meter into the top of the POS battery post. Stick the other probe as close as you can get to the VR IGN terminal. On 69/ earlier, this would be the IGN terminal at the VR. On 70 later, the "key" side of the ballast resistor.

Whatever you measure there, let's say 1.5V, is ADDED to the VR set point. So if the VR is properly at 14, then the battery is gonna see 15.5

CHECK THE GROUND PATH

The ground, too can have voltage drop. Run the engine at fast idle, with engine warm (The VR is voltage vs heat sensitive)

Stab one probe into the battery NEG post and the other hard into the VR mounting flange. The less you read the better, zero is perfect. here again, ANY voltage you measure will be ADDED to the VR setpoint at the battery. Improve grounding.

 

[Mattax]

That's both more true and less true on a '75.
More true because there are more connections and junctions.
Less true because that crazy diagram is even less representative of the routing for that year.
J1 feeds the ignition switch from the alternator output line R6. It's a longer path from the battery but a shorter one from the alternator. Just as important the current from the alternator is split before the bulkhead multiconnector.
That's all good. But it calls for a second fusible link, so that limits the loads fed by J1.
Also AFAIK '75 still has the 'engine connector' introduced a couple years earlier.
1975 schematic and photos

 

[67Dart273]

That's both more true and less true on a '75.
More true because there are more connections and junctions.
Less true because that crazy diagram is even less representative of the routing for that year.
J1 feeds the ignition switch from the alternator output line R6. It's a longer path from the battery but a shorter one from the alternator. Just as important the current from the alternator is split before the bulkhead multiconnector.
That's all good. But it calls for a second fusible link, so that limits the loads fed by J1.
Also AFAIK '75 still has the 'engine connector' introduced a couple years earlier.
1975 schematic and photos

How do we know this is a 75?

Ah yes the engine connector.

 

[slantsixdan]

1. Upgrade your charging circuit. The max available alternator in '75 was a 65A item, and those came with significantly stouter charging circuitry. Read and follow this.

2. Put in a field-loads relay to bring the regulator and alternator electrically closer and bypass all the built-up resistance in the long, half-century-old path between the hot side of the ignition switch and the regulator and alternator field terminals. See here.

3. Make sure you're buying good regulators; the one you want is this one. Good alternators, too; "remanufactured" items from the parts store (walk-in or click-on) are junk.

4. "Checked grounds" is nice, but not enough. Make sure all three parts of the system are at the same ground plane. Run a 16ga wire from the alternator housing (some of them have a round hole labelled "GRD" on the back housing—use a short self-tapping screw so it's not long enough to reach in and hit the rotor—if no such hole, just attach the wire under the head of one of the alternator's three through-bolts) to one of the regulator's mount bolts, and from there to the battery negative terminal.

 

[Mattax]

How do we know this is a 75?

Ah yes the engine connector.

Ha! You're right. We don't know that. I was going from the OP's screen name, which could be about his car, or something else entirely!

 

[carmart1975]

The blue wire going to the voltage regulator is probably your issue. All the blue wires under the hood are connected together near the master cylinder in the harness.

Follow it from the ballast resister and it will lead you to a solder joint where they are all connected. I believe that may be your problem.

Somewhere you are losing power to the voltage regulator. That is the wire that controls the charging from the alternator. Fix that wire and your problems should be corrected. That would be the first place

I’m going to check everything that you mentioned

 

[carmart1975]

Ha! You're right. We don't know that. I was going from the OP's screen name, which could be about his car, or something else entirely!

It is a 75 great observation, sir

 

[carmart1975]

I do want to mention I have a super beefy shunt wire. I don’t know if that has anything to do with it, but I thought I would put that out there.

 

[carmart1975]

I think I found the problem and how shall I go about fixing this?

 

[Mattax]

One question down.
A few more to go. LOL
Because its no longer stock, and we don't know know where things have been tied in, modified, or where the voltage is being measured.

There standard wiring scheme is like this

But cars with rear defrost, and maybe other options came with a heavy duty scheme.
See the link I posted earlier.

Shunt.

There's a recent thread where someone pointed out the downsides of using a shunt. There are upsides too. In any event, it may or may not have just made diagnosing more difficult because we have to either guess the current paths or you do some voltage and current measurements.

67Dart273's point about the regulator sensing a lower voltage remains valid. Take your finger and follow the path to the regulator;s sense terminal. The more current sharing that path, the more voltage loss.
change in Voltage = Resistance x Current.

The big high rated alt may or may not help at idle rpm. Those ratings are always at some high rpm.
One hting it most certainly will do is draw more current to created the magnetic field. So the wiring to the field needs to be up to that task. The regulator also needs to be up to that task. In my experience the MP P part VR does not due will with even the revised squareback's field current.

I'd start by ditching the electric fan. Put a more normal alternator on it, and then diagnose.

One last thought. Battery condition can effect the charging too. Dana recently had a thread about this.

 

[Mattax]

I think I found the problem and how shall I go about fixing this?

View attachment 1716371697

Is that black wire a hack splice?
Generally. The factory either used a welded splice or figured out a way to daisy chain with two wire junctions.

You want to do it right?

Search FABO for Chrysler wire terminals, and Wire crimping. The type of crimp terminals used called open barrel, or some companies call the ones with insulated supported wings "F type".

You'll want to draw and or photograph the wire positions.
Then remove the terminals from the connector. Use a slim tool (make one from a cotter pin if you're in a rush). Evaluate and go from there, on what type of repair is best. Might decide to take it back and splice in new wire with heat shrink and new double wire Packard 58 type terminals. Be sure the terminals match the wire gage.

 

[carmart1975]

I do remember before I put an E fan on it and upgraded the alternator. It always had a voltage bouncing problem. The car was factory equipped with air conditioning so I assume it was a 60 amp alternator stock so that’s probably one that i took off then I replaced it with another 60 amp put my electric fan on and at idle and drive with the headlights on and heater on it would completely stall out because of the draw I put the power master 95 amp in no problems at idle, but still had the voltage bouncing. It’s been charging at 15 V since I bought the car Before I modified anything.

 

[Mattax]

if its been 15 V at the battery its borderline overcharging.
If its 15 V somewhere else, then we're just guessing

 

[carmart1975]

Is that black wire a hack splice?
Generally. The factory either used a welded splice or figured out a way to daisy chain with two wire junctions.

You want to do it right?

Search FABO for Chrysler wire terminals, and Wire crimping. The type of crimp terminals used called open barrel, or some companies call the ones with insulated supported wings "F type".

You'll want to draw and or photograph the wire positions.
Then remove the terminals from the connector. Use a slim tool (make one from a cotter pin if you're in a rush). Evaluate and go from there, on what type of repair is best. Might decide to take it back and splice in new wire with heat shrink and new double wire Packard 58 type terminals. Be sure the terminals match the wire gage.

It is for sure a hack place and I’m just going to do a quick fix for now to see if it fixes my problem then I’ll do it right

 

[carmart1975]

if its been 15 V at the battery its borderline overcharging.
If its 15 V somewhere else, then we're just guessing

To be exact, it’s 15.5 at the battery constantly at idle or with RPM

 

[Mattax]

Well without the ammeter we can only assume its been overcharging

Anyway here's some engine bay photos (standard wiring).

6. Cylinder duster is now a 340 ignition issues wants to start when you let up on the key

I've done some research on this. Still can't find what was actually the problem when people had this issue. With a test light hooked up to the ballast resistor I turn the key on. I have light when I turn it to start. I have no light.. so I went to my ignition plug on the column and found that...

www.forabodiesonly.com

 

[carmart1975]

so I tested the blue wire voltage at the resistor and the blue wire voltage at the back of the alternator field wire both came back at 13.8 while the car was running so clearly there’s no loss right then I put a voltmeter to the battery and the back of the alternator both came back at 14.8 and then with a heavy load 15.8 i am stumped I checked all the wiring and everything looked good.

 

[Oldmanmopar]

I think I found the problem and how shall I go about fixing this?

View attachment 1716371697

What did you do to fix this problem. That blue wire is one of the wires that goes to that solder joint. Did you cut the harness apart and find the solder joint. Seeing that wire you pictured makes me think that will be your problem.

The only way to find it is to follow all the blue wires .

 

[carmart1975]

I took apart the whole wire loom that goes across the engine compartment to the passenger side. I could not find any solder joint that you were talking about. The only thing that looked messed up was the thing that I pictured and here’s a picture of how I fixed it temporary to see if it would fix it.

 

[67Dart273]

This has GOT to be a voltage drop problem. If you can duplicate operation under a fairly heavy load, or maybe just jumper the fan to run for a period while you are measuring, chase the VR IGN wire through it's terminals to the ignition switch and back to the battery. The blue. You might find drop EG on both sides of the bulkhead connector. You might find drop between the terminals of the ignition switch. If so, one way around it is to activate a relay out in the engine bay by cutting the blue and feeding it to trigger the relay. Feed the relay contacts power from the start relay "big stud." Hook the other end (engine bay end) of the blue to the switched contact of the relay.

 

[Oldmanmopar]

The schematic pictured above shows all those blue wires connected together before the regulator. Did you find that connection where they are all soldered together? It has to be there somewhere. Where does the blue wire go from the regulator?

It has to have a power source. It comes from the ignition switch but before it goes the regulator it splits off and goes to the Alternator, ballast, and choke thermostat, You have to have that soldered splice in the harness somewhere or how would it reach all 4. You must not have looked very well or your harness has been changed around.

Testing You can take 2 wires from the voltage regulator blue wire. One to the battery and one to the alternator blue wire.. That should correct the charging for a test

 

[67Dart273]

The schematic pictured above shows all those blue wires connected together before the regulator. Did you find that connection where they are all soldered together? It has to be there somewhere. Where does the blue wire go from the regulator?

It has to have a power source. It comes from the ignition switch but before it goes the regulator it splits off and goes to the Alternator, ballast, and choke thermostat, You have to have that soldered splice in the harness somewhere or how would it reach all 4. You must not have looked very well or your harness has been changed around.

Testing You can take 2 wires from the voltage regulator blue wire. One to the battery and one to the alternator blue wire.. That should correct the charging for a test

Actually Steve, the real problem is usually the supply TO that junction. Either dropped supply to the ign switch, or the connector, the switch itself, or the bulkhead connector terminal for the blue

Easiest fix is to stick a relay in that circuit