randyta

Battery Problem on 36 Plymouth?

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My Plymouth has a 6v system with a generator.  Normally, when I start the car the amp meter goes to a +20 charge for a short time then back to 0.  What you would expect.  A few days ago, I noticed that while driving, the amp meter is showing a +10 charge and just stays there.  If the engine goes to idle, the amp meter goes back to o.  Once moving again, amp meter back to +10.  Thought it might be a bad cell and had the battery checked out three times yesterday and all checked out o.k.  Battery is a three year battery and is 5 years old.  Could this be a cell that is going bad but just hasn't totally gone bad yet and not showing on a tester?  The generator and voltage regulator seem to be working fine.  Any ideas would be appreciated.

 

Thanks,

Randy

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Not a direct response to your question, but the last thing you want to do for good battery health is to drive around constantly with a 20 amp charge going into an already fully charged battery - you'll boil the water out and warp the plates in no time.  That is why folks of that era drove during the daytime with their headlights on - to sop up the unwanted charge.  All that changed around 1936/37 when true generator regulators appeared which tailored the charge to the demand and condition of the battery.

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   If I’m not mistaken, I believe you’re right—a weak cell, on a 6V or a 12V, battery may check out OK on a static test, but under a load test, that weak cell will present itself with a drop in load capacity.

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Thanks for your insights.  Replaced the battery but still have the problem.  Will drive it for a week or so to charge it to full and see if that helps. If that doesn't fix it will pull the generator and take it to someone that can check it out and repair it.

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My recollection is that 1936 Plymouth P1 model still had simple circuit breakers, while P2 models had early voltage regulators. Just out of curiosity, which model do you have?

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The generator is only doing what the voltage regulator tells it to. New battery should be charged before putting it in the car. 

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1 hour ago, randyta said:

Thanks for your insights.  Replaced the battery but still have the problem.  Will drive it for a week or so to charge it to full and see if that helps. If that doesn't fix it will pull the generator and take it to someone that can check it out and repair it.

 

 

You have not mentioned if you have a volt meter?

 

You cannot really diagnose a charging system without an accurate voltage tester.  Forget the ancient amp gauge for now; find out what the volts are showing at idle as well as various RPMs up to cruise speed.   Volts will tell more info than amps in "this" case.

 

.

1 hour ago, Mike36 said:

The generator is only doing what the voltage regulator tells it to.

 

True, in most cases.  I would not send out the generator at this point either, without testing the voltage.   Our stuff is old and strange things can happen like frayed field wiring that might cause generator issues.  But without a voltmeter, we are assuming the amp gauge is OK, and that is faulty diagnosis procedure.

.

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On ‎4‎/‎6‎/‎2017 at 1:38 PM, Mike36 said:

The generator is only doing what the voltage regulator tells it to. New battery should be charged before putting it in the car. 

If I felt the need to caption the whole business, I'd say that the battterie's resistance to additional charging is what tells the circuit breaker or voltage regulator what to do, which in turn "tells the generator what to do."

Edited by Hudsy Wudsy (see edit history)

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My P2 does have a voltage regulator attached to the generator.  I also have a volt meter but not sure where to attach the leads.  Do I attach one to the generator output lead and the other to ground?

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46 minutes ago, randyta said:

I also have a volt meter but not sure where to attach the leads

 

 

Put the voltmeter right at the battery terminals;

 

-then get an accurate reading of the voltage before starting the car. 

 

-then start it and run the engine at RPMs around what it would be at 40 mph.  Run it for at least a minute or so at that speed to get an accurate reading.

 

-also, after that high RPM reading, then let it go back to normal idle and get that reading after a minute or so of at idle.

 

report back with what you had.

 

.

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The use of "circuit breaker" in the above discussion, you are meaning the generator cut out relay? Circuit breakers are to open a circuit when too much current is drawn to prevent fire.

 

Voltage regulators look at voltage (and the three coil types also look at current draw) and vary the voltage going to the field terminal to control charging.

 

Generator cut outs are used for three brush generators and others with fixed outputs, to keep the battery from going dead when the engine is not running.

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My 1937 Dodge pickup had the three brush generator with cut-out relay setup.  The generator is always charging the battery with this configuration.  The third brush setting is adjustable to the voltage output desired to keep the battery charged but not overcharged.  When the truck was running the battery was getting charged all the time and the ammeter showed that by indicating a + movement on the amp gage.  The cut out relay is mounted to the gererator case so it's easy to identify this setup versus a firewall mounted voltage regulator.

 

The description of the charging system in the original post does not sound like it's a three brush generator and cutout, rather its more like a generator with separate firewall mounted regulator.  It also sounds like there may be some type of load on the electrical system that is drawing current to make the ammeter behave as reported.  I would want to first verify there is no current draw with the key in the off position that might be slowly discharging the battery.

 

Terry

Edited by TerryB (see edit history)

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1 hour ago, Frank DuVal said:

The use of "circuit breaker" in the above discussion, you are meaning the generator cut out relay? Circuit breakers are to open a circuit when too much current is drawn to prevent fire.

 

Voltage regulators look at voltage (and the three coil types also look at current draw) and vary the voltage going to the field terminal to control charging.

 

Generator cut outs are used for three brush generators and others with fixed outputs, to keep the battery from going dead when the engine is not running.

Yes! I apologize. I shouldn't post when I'm sleepy. Cut out relay is exactly what I should have been saying. Thanks for straightening out the foggy old guys memory. Also, Terry, it's perceptive of you to determine that this is a voltage regulator equipped car from the first post. From this point on, listen to Terry, not me!

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Finally back,  Took my generator, which has the voltage regular attached, to a repair guy and after testing everything said that I need to replace the voltage regular.  Question now is where can I get one.  It is an Autolight TC-4301-A 6v + ground.  Anyone have one they would like to part with or can give me a hint on where I might find one?  Already looked on Ebay.

Thanks for your help.

Randy

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Another option if  you are anywhere near farm country is your local NAPA dealer, or local independent auto supply store (not the chain stores).

 

Lots of stuff still around that's 6 volts and they can match you up if you take your old one in and look for the oldest guy at the counter. An old time farm equipment dealer could probably help you out as well. The new farm box stores carry them but technical assistance is usually non-existent

 

this will get you one that works but it will not be exactly like the one you have, but it will work fine..

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I have the same car as you      not really understanding your problem     E mail me     bobnroman@yahoo.com     with your phone maybe I can help

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In your pics I saw the voltage regulator was mounted on the back of the generator, interesting setup for sure. The cut out relay I mentioned is mounted the same way but is only 1/4 the size of the regulator you have.  Can your reg be rebuilt?  I have heard it's possible but not sure who does it.

 

Terry

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Thanks for all your help guys.  Found a replacement regulator and hope it resolves my problem.

Randy

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On 3/29/2017 at 8:52 AM, Owen_Dyneto said:

Not a direct response to your question, but the last thing you want to do for good battery health is to drive around constantly with a 20 amp charge going into an already fully charged battery - you'll boil the water out and warp the plates in no time.  That is why folks of that era drove during the daytime with their headlights on - to sop up the unwanted charge.  All that changed around 1936/37 when true generator regulators appeared which tailored the charge to the demand and condition of the battery.

I've heard of folks doing that.  Except my Grandfather would not have done it because he would say it used too much gas. 

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