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Complete confusion over 6 volt. Please advise.


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Hello everyone. I am new to this forum, and I am the owner of a 1941 dodge D19 luxury liner sedan.  I purchased this car last July, and, while it moved under it's own power, it was far from roadworthy. I have since been working on making it safe (and daily driveable, as crazy as it sounds) for the last 11 months.  I have opted to tackle the project of bringing her back to life, but it had been a little bit of a challenge for me... this car is way before my time (57 years befor I was born!) and therefore I have a few questions that may seem like basic knowledge, but confuses the heck out of me! 

 

However, she made her first voyage yesterday, a 15 minute drive from the shop to my house. Now that I am seriously looking at the final phases of getting her roadworthy again, something crossed my mind. As far as I know, these dodges were 6v positive ground. This appears to be an all original system, so I am going to assume it is still positive ground and not a 6v negative ground system. 

 

When I purchased the car, it moved and drove (with a cracked radiator) but had no headlights/tail lights, dash lights, horn or fuel guage.  The owner had a 6v battery in it.  I have since rewired and replaced all the exterior lights, and put a new 6v battery in it.  When I replaced the battery, I installed it the exact same way as the last owner, with the negative cable on the negative terminal and positive on positive. I then replaced the OEM headlight switch with another OEM one, but could not get the headlights to work no matter how many grounds I cleaned or how many times I double checked the wiring. I ended up tapping into the ignition switch and they work like a charm, the switch is functional with the car running but if i turn the ignition off, he headlights will turn off as well. But now I am second guessing it after realizing my positive ground system, could the switch initially being non-functional be related to my battery being hooked up as neg ground? The horn has actually worked only one time in 11 months, but every other time all I get when I press the switch is a metallic "thunk" noise like the relay, but no horns. 

 

Now the big reason I am questioning this is, my amp meter appears to read backwards. When I start the car and rev it, the amp meter will go down.  When I press the horn, even though it doesn't work, and the relay clicks the amp meter goes up. Before I drove it back to the house, I tested the voltage and it was getting 7 volts...from a generator at idle?  I made the drive successfully, but about two blocks from my house the generator began whining, and when I popped the hood I noticed smoke coming out of it.  I then realized that the generator had oil caps (DUH!) And I filled it with about 6 drops of oil. I only saw one fill on the top as far as I know.  Fast forward to today, I start it for the first time after dropping oil in it, and it makes the same squeal for about 10 seconds before quieting down completely again.  Although I did not run it for more than about a minute. I will check the voltage again tomorrow.  

 

So, now after thinking about the positive ground stuff (especially the backwards amp meter) I am totally confused about several things.  Could the electronics not have been working because the battery was installed neg cable to neg terminal?  If everything seems to work now, besides fuel guage and horn, do I even touch it?  Is the fuel guage not working because of another component or the wiring issue? Is that why the generator began to smoke and squeal, or is it because it was out of oil?  And finally...is it really as simple as draining the battery, recharging with the positive lead from the charger on the negative terminal, and then reinstalling the battery with the pos cable on neg terminal? Or do I have to switch wires on the generator too?  I am fairly nervous now, thank you in advance for all your help. 

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You're uncertain of polarity? It will give you diagnosing difficulties. Forget polarity for a moment and follow ground battery cable. Where does it lead to? pos or neg. Then work form there. Originally pos was grounded. 

Generator smoking is not due to lack of oil. It can smoke if polarity reversed and may short. Squealing may be loose fan belt.

 

After checking your battery is connected correct, polarize generator. If it's not shorted, amp meter will move to Charge when revved.

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Lots of questions here. I suggest you nail down a few simple things first. 
 

Find the positive post on your battery. Follow the battery cable. Where does it go? 
 

A battery is a battery. You don’t hook a Mopar car battery up backwards to your electric battery charger in your garage to charge it. You hook the garage battery charger red cable to positive when charging it. Black to negative. Same as any other battery. 
 

The word “ground” just means the return path to the battery. The old mopars used the positive battery post and the frame of the car, as the return path to the battery.  
 

A Circuit is a circle. Amps leave the battery at 1 post but have to make it back to the other battery post, completing the circle (or circuit). As you can probably guess, with most other cars,  the amps leave the positive post, do their thing (like lighting up a headlight bulb) then return via the ground path to the negative battery post. 
 

Mopars do it different. The amps leave the negative post. Light up a head light, they return back to the positive battery post via the ground path. Which happens to be positive. 


Confused yet? I think I am. 

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Mopar was not the only company to use positive ground 6v batteries.  In fact most car companies before 1956 were 6v positive ground, including Ford.  GM was different because they used 6v negative ground systems.  

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First off, unless your car has a radio it has no electronics.  It's electrical system, with the exception of the generator and regulator is insensitive to polarity.  The headlights and headlight switch neither care nor know which way they are hooked up, nor do the horns.  Assuming you don't have LED head lights.

 

So, rather than consider the issue in total and feeling overwhelmed let's take it one section at a time.

 

Verify the battery positive is connected to the battery cable that is bolted to the engine.  Verify that he battery negative is connected to the starter.

 

Once we sort that we can move on to another section.

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7 hours ago, MarcDeSoto said:

Mopar was not the only company to use positive ground 6v batteries.  In fact most car companies before 1956 were 6v positive ground, including Ford.  GM was different because they used 6v negative ground systems.  

Sorry, but all GM except Chevrolet before 54 had positive ground 

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GM before 54 were Negative ground.     It is possible in Luxury Liner's case that someone has reversed the ammeter connections.   As stated above,  Start at the beginning.  Connect the battery with the positive terminal grounded.   Polarize the generator by fastening a clip lead to the BATT terminal of the regulator and brushing the other end across to the ARM .  A few sparks and it is done.  It is then safe to start the engine.    Other components in the car are not polarity sensitive except the radio which will work but not as well.      A correctly function ammeter will prove that all is well.

 

Warning :   It is possible to reverse charge a battery.  Check with a multimeter that the POS and NEG posts are what they claim to be.   If this is the case, the battery must be completely exhausted before a recharge is attempted.  This is a job for someone who knows how.

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The lheadlight might not be working becasue there is a fuse built into the switch like on my 39 Desoto. It is a little metal tube that hangs down from the body of the switch. The fuse might be missing or blown and bad. Will need to check that first. replace if the fuse is missing and or broken.

 

I have a 39 Desoto so our cars willbe similar to each other.

 

Rich Hartung

desoto1939@aol.com

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8 hours ago, MarcDeSoto said:

Mopar was not the only company to use positive ground 6v batteries.  In fact most car companies before 1956 were 6v positive ground, including Ford.  GM was different because they used 6v negative ground systems.  

 

53 minutes ago, chrysler1941 said:

Sorry, but all GM except Chevrolet before 54 had positive ground 

 

6 minutes ago, dpollo said:

GM before 54 were Negative ground. . . .

Off topic for this thread, but GM seemed to be inconsistent in the 1920s and 30s with some years of some makes positive ground though the general rule seemed to be negative ground for them.

 

I guess now that I’ve made this bold statement I should dig into the documentation I have to find what years of what makes were positive ground. . .

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53 minutes ago, TodFitch said:

 

 

Off topic for this thread, but GM seemed to be inconsistent in the 1920s and 30s with some years of some makes positive ground though the general rule seemed to be negative ground for them.

 

Inconsistent is good word for GM.  For instance 49-early55 Chevy and GMC trucks were nearly identical in appearance.  Different engines and grille but otherwise same.  Except, GMC was positive ground, Chevy negative.  Nearly as confusing as LH lug bolts and/or nuts.  Yeah, GM did that on some makes too

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Your headlight switch was I believe was originally powered from one of the ammeter terminals.  It should have as mentioned a fuse integral with the chassis of the switch.  This is a 30 Amp fuse ass except for the dome light all lighting circuits pass through the switch.

 

With the battery in and connected as designed negative to starter and positive to engine as ground, with in switch in the off position get in and step on t he brakes.  Does the brake come on? If so which way the the ammeter needle move with the brakes applied?  If it goes to minus, the battery is installed correctly.

 

This is where a test lead or jumper wire come in handy. Take a piece of 6 to 8 feet of 12 gauge automotive wire and put an insulated alligator clip on each end. With one end connecter to the minus battery post, you can power your individual lamps and junction straps independently, which will indicate they are functioning, and through the process of elimination, isolate where the problem lies.

 

Don't forget the headlight dimmer switch as the source of lighting problems. Corrosion on the elements there can shut down all forward lights.  Here is where you can test the component with the test lead.

 

Run the wire from the battery to the in terminal of the dimmer.  This should either light the lights or send power  to the lighting terminal block on the inner fender or radiator support. If not the dimmer is the culprit as you know it's getting power. Many times the dimmer will self clean it's inner  contacts by cycling it a dozen times or so..  Then you can back up to the switch and knowing it has power in to the switch, you can probe the out terminals to assure the switch is operating is it should.

 

Forgot to mention equip your test lead with an in line fuse holder and 20 Amp fuse.  Either Glas tube or the blade type is fine.  As stated above most things are polarity dumb.  It's like going to grandma's over the river and through the woods or through the woods and over the river.

Edited by greg g
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Hello, 1941luxuryliner,

i use as a daily my 1941 dodge club coupe for 10 years now and i have a lot of manuals and books about this car, plus  my knowledge and experiences with my car on the road.

Like it was said before, check the fuse under the light switch, the fuse holder is like a small bullet with a 1/4 of turn lock.

 

about the generator, first thing you can do is open it and check the brush first and cleaning inside old the 80 years of dust and grease. on the armature, clean very very carefully and softly the copper where the brush lies to have it clean but to keep surface regular as possible. and with a thine saw blade cut like a little hook at one end, cure softly the mika between each copper post.

with this done first and unless the armature have an internal probleme itself, you start with a "good" generator.

 

reassemble it, put it in the car.

 

 then polarize it as follow

 

remove the belt and disconect the wires armature and field on the generator.

 

with a piece of wire, ground (+) the field post and to finish the polarisation, with another piece of wire connected to the negative post of the battery, connect it to the armature post of the generator.

a spark will occure at the connection it's normal and the generator will turn as electric motor. the polarization is done for a positive ground system like our cars.

 

if the wiring harness is original, there is no reason the polarity on the equipments is reversed cause the grounds of them is made by the body.

so the ameter should go up when you rev the engine. and if you ahve a good battery it should stay close to zero whatever you turn on in the case you have a good working regulator.

 

feel free to send private message for technical books if you want.

 

about the horn, the seating you have to remove the cover. if you have dual horns, disconet one to set the other. but before touching everything, just clean the points softly to see if they work and if not play very very lightly with the seating screw, a very very small tiny turn will make big difference.

 

hope this will help a little for you and other in need of help.

 

Adrian.

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Wow, thank you so much everyone for the responses!  I have a few updates, as well as things to clear up that I may have been unclear about.  My exterior lighting does work now, initially they did not.  The headlight fuse was good and the dimmer siwtch worked. So I replaced the headlight switch with a NOS unit. That also did not fix it, and I had the wires correct and the ground clean. So I ended up tapping into the hot wire from the ignition switch (as the hot wire for the headlights looked good, but just wasn't getting any power for some reason) and they have been functioning ever since.  That was about 6 months ago. 

 

Fast forward to today, where I am trying to solve the 6v/ smoking generator issue that came up on its first drive last week. I went and checked the battery cables as instructed, and it turns out that I DID actually have it hooked up backwards!  The guy who sold me this car hooked up the battery with the black cable to the negative battery terminal and the red to the positive terminal, so I (foolishly) followed in the same direction. However, the red cable goes to the starter and the black goes to the engine block ground.  So seeing as it is positive ground, they should have been reversed.  

 

I reversed the cables, then attempted to jump the ARM and BATT terminals before starting, and I believe I did it correctly though I could be wrong.  After removing the voltage regulator cover, I held a piece of wire to the ARM terminal and brushed it over the the BATT terminal on the regulator, and got the expected spark. I started the engine, and now the amp guage works as expected!  Previously, it was backwards. If I pressed the horn or brake lights, the amp meter would raise, and it would drop as the engine was revving and it was charging.  Now, after today, it reads as it should, going down when an electrical load is applied and also raising while revving. 

 

So I believe I am headed in the right direction, after reversing the cables and ensuring the positive terminal is grounded, the amp meter now reads correctly. I only have one final problem. The generator still has a nasty whine to it, even after oiling the port on the back side too.  After about 15 seconds of running, it became hot to the touch and began screeching again. About 45 seconds after that, it began smoking out of both ends.  That's when I shut the engine off.  I'm thinking the generator is toast, I dont know if it was between me and the previous owner running it with the cables on backwards, or if it was from the lack of oil in the generator, but either way it is still smoking and still screeching after a few moments of running. Although for some reason, the amp guage still raised when I revved it, even while smoking and screeching. So I assume it is still charging, but possibly a bad bearing? Either way it does not seem like a good sign, perhaps it is time for a rebuild? 

 

I just want to make sure I'm headed in the right direction and all seems well before I go rebuilding the generator. I took a video clip but cannot post it in here due to the size.  Thanks again for all the help and especially the quick responses. I am curious to hear your suggestions and feedback

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Is the smoke, an electrical smell or an oil burning smell?  If its an electrical smell, have the generator rebuilt, if oil, there probably is some oil dropped into the generator that is burning off.

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2 hours ago, maok said:

Is the smoke, an electrical smell or an oil burning smell?  If its an electrical smell, have the generator rebuilt, if oil, there probably is some oil dropped into the generator that is burning off.

It is more of a burning smell of something rubbing with resistance- it sounds strange but it almost smells similar to how a clutch would smell if it was burning.  It began smoking on the first drive home from the shop last week, it sounded totally normal the whole time (3.5 miles, as well as all of the short runs the engine did during the last 11 months) up until the last few blocks before my house, where it began audibly screching/ whining.  I pulled home and popped the hood to find the generator smoking. That was before I added oil, so it is not the oil burning off.  Again, that was last week, so I was still running with the battery installed backwards (which I corrected today.) As for the smell of the smoke itself, it does not have an "electrical fire" burning smell like a wire burning, and all the wires are cool to the touch, but the generator quickly gets very hot. The smoke comes from the generator itself, out of both ends, after roughly 45 seconds to 1 minute of running.  

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Could be a bad ground with the smoking generator, been there.  Rebuilt the generator on our Terraplane a while back, went for a test drive and after a bit was being followed by smoke and that burning clutch smell.  When I checked everything, I discovered that I had not cleaned the ground connection to the generator well enough after painting the unit.  Remedied and no problem since.  These 6v systems require really good, clean connections.

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