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8 Volt Negative Ground???


edrendek7777

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So I figured I would start a new post on this...  My 50 Plymouth wont start at all, tried to charge the battery and still nothing.  So I am looking to install a new battery and used generator from a donor car I have, also a 50 Plymouth.  My issue is that the existing battery is an 8 volt negative ground.  And I want to install a 6 volt positive ground like it is supposed to be.  Can I just put the new battery in the car with the positive ground?  I can check the polarity of the generator or whatever else I need to do.  But will this work?  I have no idea why it is negative ground and if this caused issues with the existing battery.  I literally got the car a few days ago, drove it around fine for an hour or so, stopped and started several times, then the battery is dead.  Please let me know.

Thanks in advance.

Ed

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I recall in your prior threads that the book is more geared around bench test than in the car.  Well to some degree it does but you need the verify the condition of the generator, if it will not motor, it will not charge...is a good place to start.   Do inspect for leading of the commutator...if you find this condition..it is shot....unless you know a shop that can rebuild your armature.  Often a cost beyond a replacement know good unit.  Prove one component at a time, generator, VR and wiring between, good battery, polarized correctly for the orientation you prefer.  If you charge your battery and it goes dead just sitting on the bench a day or so later....shorted internally....will not work on a 6 volt application as they need lots of current...why the industry went to 12 volts.  Less current lighter wiring.  

 

Odds are the original VR was tweaked to get 8 volts out of your generator...a band-aid fix to a problem even then.  Wrong size cabling and or voltage drops kill lots of these 6 volt systems quickly.  A voltage drop tells a lot, a visual of a cable just tells you it is a good candidate but only proven by the voltage drop test.  Clean tight connections are your friends.  

 

Start from the beginning, use you book, read the entire section...lots of good tips here and enough to get you by with in car testing....at least to the point you can make a good call on component to address more in depth.

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I have a generator and regulator that should be just fine and are from a 6 volt positive ground car.  I also have a new 6 volt battery to use.  I also have a very local place that can and probably will rebuild my generator and or regulator if need be.  I started reading my manual last night and will probably finish up and reread tonight just to be informed.  I will have an experienced hand helping me Sunday morning to fix these issues, hopefully.  I can check the polarity of the generator or whatever else I need to do. 

 

Simply put, can I just put the new 6 volt battery in the car with the positive ground?  Even though the existing battery is 8 volt negative ground?  Or should I not do this?  Will this work?

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15 minutes ago, chrysler1941 said:

Have I understood it correctly, you have the original 6 volt system and wondering why an 8 volt battery has died??

Essentially yes.  I think anyways.  It does not appear that anything is new or newer that has been changed to 8 volt.  Also wondering what will happen if I pull that 8 volt negative ground and hook up a 6 volt to positive ground to the vehicle? 

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putting a 6 volt battery in place is just a matter of popping in a 6 volt battery..and you can run it temporary if first attention is give to backing the regulator back to 7.2 - 7.5 volts.  You do not wish to extend the running period at higher output with the 6 volt battery in place IF  you wish to back the regulator down that is in there now supporting the 8 volt battery and keep that VR in play.   In regard to system transfer of all 6 volt items, gen, VR and battery, again a bolt in...verify that your polarity is correct and proceed from there.....

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2 minutes ago, Plymouthy Adams said:

putting a 6 volt battery in place is just a matter of popping in a 6 volt battery..and you can run it temporary if first attention is give to backing the regulator back to 7.2 - 7.5 volts.  You do not wish to extend the running period at higher output with the 6 volt battery in place IF  you wish to back the regulator down that is in there now supporting the 8 volt battery and keep that VR in play.   In regard to system transfer of all 6 volt items, gen, VR and battery, again a bolt in...verify that your polarity is correct and proceed from there.....

 yes and polarize the generator on regulator when switching to positive ground before start.

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It's possible that your VR wasn't modified for the 8 volt battery and still outputs 7'ish volts and hence why your battery is going flat. If this is the case, then you could pop in a 6 volt battery, flash the generator for +ve ground and bob's your uncle.

Even if your VR has been modified for 8volts, there wouldn't be a problem with running 6 volt battery. But do have it modified back to 7.5volt output.

 

There maybe other reasons why your car isn't starting though.

 

 

Edited by maok
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If you are going from neg to pos ground, connect the pos and neg wires correctly, flash or polarize the genny,  and give it a whirl. Also check the amp gage if it is reading backwards after doing this you need to reverse the wires at the amp gage to read correctly. 

 

 

Joe Lee

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The charging system and the engine not running are two separate problems.  An engine will run quite q while without a charging system, the charging system won't work at all without a running engine.  What is your priority?  What tests have you performed on the engine to trouble shoot the no start , no run situation?  Does it have compression, is it getting fuel, is it getting spark and at the proper time??  An engine with stuck valves, a common problem when these engines sit for a while won't start regardless of how many volts you throw at it.  An engine with a distributor with incorrectly spark plugs and leads won't start, an engine that has out of time ignition won't start.a an engine that isn't getting fuel to the carburetor won't start, an engine with a collapsed or blocked exhaust system won't start.  If the engine won't start and run all the work on the battery , generator and regulator don't matter.  If you are just cranking the engine and have no accessories it don't care if it's six volt 8 volt or 12 volt positive or negative.  If it's in a condition to start it will and run till you turn it off.  

 

You would be ahead of the game in getting it starting and running, then worrying about electrics.  You can jumper  wire the coil, and energize the solenoid with an old pair of pliers to get it going if it will go it will with simple work arounds..

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   Check the fuse coming off the key switch. And check the wires on the back of the Amp gauge. I'm guessing that, stopped starting and charged battery, mean that it doesn't turn over. Look at the coil wire connection to the Distributor, if the coil is marked POS., then it's POS. ground. And the battery was put in wrong.

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OK, so if the battery was just put in wrong, negative ground instead of positive ground, would it drain the battery when running instead of charging?  I replaced the generator and battery from my other donor 50 and it started but still was draining the battery, then it stopped starting all together.  Sounded like the starter was going.  Bendix was slipping just when it was about to start.  If I just put the batter back the way it is supposed to be, positive ground, polarize the generator, then it should be good?  I tried to polarize the generator and per the resources that were posted here, it said there should be a minor spark when touching the wire to the correct spot on the VR, but there was no spark... so not sure that the generator actually got polarized correctly.

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Does the Ammeter needle move at all, + or -, when electrical loads are applied?

May be time to break out the volt meter and do some testing. Do you have 6 volts at the BATT terminal of the voltage regulator? Are you getting any voltage output from the generator when running? 

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1 hour ago, edrendek7777 said:

OK, so if the battery was just put in wrong, negative ground instead of positive ground, would it drain the battery when running instead of charging?  I replaced the generator and battery from my other donor 50 and it started but still was draining the battery, then it stopped starting all together.  Sounded like the starter was going.  Bendix was slipping just when it was about to start.  If I just put the batter back the way it is supposed to be, positive ground, polarize the generator, then it should be good?  I tried to polarize the generator and per the resources that were posted here, it said there should be a minor spark when touching the wire to the correct spot on the VR, but there was no spark... so not sure that the generator actually got polarized correctly.

Field and Armature of generator can burn if subjected to opposite voltage.

Generator and battery from donor but what about VR? 

You need to individually diagnose these 3 parts separately. 

 

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  • 7 months later...

A few posts back, soth122003 posted a video showing how to polarize the generator. This method of polarizing is correct for Fords but wrong for Mopar vehicles. To polarize a Mopar generator use a jumper to momentarily touch the Battery terminal on the VR to the Armature (Generator) terminal on the VR. 

http://p15-d24.com/files/file/16-flashingpolarizing-generator-guide/

 

 

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On 8/28/2019 at 8:11 AM, edrendek7777 said:

So I figured I would start a new post on this...  My 50 Plymouth wont start at all, tried to charge the battery and still nothing.  So I am looking to install a new battery and used generator from a donor car I have, also a 50 Plymouth.  My issue is that the existing battery is an 8 volt negative ground.  And I want to install a 6 volt positive ground like it is supposed to be.  Can I just put the new battery in the car with the positive ground?  I can check the polarity of the generator or whatever else I need to do.  But will this work?  I have no idea why it is negative ground and if this caused issues with the existing battery.  I literally got the car a few days ago, drove it around fine for an hour or so, stopped and started several times, then the battery is dead.  Please let me know.

Thanks in advance.

Ed

So I I just got my 54 Savoy and it was set up the same way. I just put a 6v battery back in it and adjusted the regulator back down and all is good. If you're switching back to positive earth just reverse the polarity on your generator. I left mine negative earth just because I work on cars for a living and old habits die hard and I dont want to short something out on accident.

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It's entirely possible that the person who put the 8 volt battery in the car had no idea what positive ground is and just put the battery in backwards, it's happened before.  Most stuff on these old bats don't care much about polarity, even the old radio will work fine, but if the ammeter shows discharge as RPM's increase, and appears to be charging at low RPM's, then some idiot put the battery in backwards.  Are you even sure they bothered to adjust the voltage regulator?

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