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1941 Special Battery Charging issues


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I have a 1941 buick i was given from my father many years ago. Recently the car would not start so i replaced the 6V battery with a new one. I believe the new battery is NOT charging. I dont see a charge on the in dash ammeter. I measure 6.15 Volts at the battery with the car off and the same with it running at high idle. If i ground the field at the VR i still get the same voltage. If i turn on the headlights the voltage drops to 5.5 V. I dont see a change in voltage at all. I dont have an ammeter to hookup in series between the Bat lead on the VR to see if i am getting current. I just remember the dash showing a charge when i was at high idle before. Is this a VR problem or generator. The generator is not that old since last rebuild. How can i narrow the problem down closer.

Thanks

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First thing to do: since you replaced the batt, polarize the gen. Put a screwdriver momentarily between the "Batt" (or "A")  and "Gen" (or "B") terminals. Your symptoms look like that may be it.

 

If not, do you have the shop manual? If so there is a nice writeup in there that will get you to the answer. Other possibilities: cutout not working correctly/maladjusted, points in the VR oxidized. I am guessing the gen is OK since it was worked on recently but the TS from the shop manual will reveal that.

 

Cheers, Dave

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Thank you for the advice. I will try the polarizing today. Any reason why after changing the battery the system would de-polarize? Yes everything worked until the battery went bad and i replaced it. I do have a hard copy of the shop manual and the only issue is i dont have an Ammeter that can handle any significant current so i was trying to troubleshoot with a voltmeter. My voltmeter can handle up to 10amps as an Ammeter and is unfused.The shop manual seems to require an Ammeter for all troubleshoot procedures.

 

I will try the polarizing shortly, that seems quick and east.

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Update: 

I shorted the Batt "A" to the Gen "B" and saw a little spark. I did not see any change. The battery is still always discharging. If i turn the lights on while its running, even at high idle or reving it up it is pegged at the discharge side.

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You should determine whether it's the generator or the regulator that's faulty. Ground the field terminal on the generator (momentarily) and see if it goes to full charge on the ammeter. If so, the generator is OK and it's probably your regulator. If not, the generator likely needs to be repaired.

 

A healthy generator should pretty much keep everything at 0 once the battery is charged. It should show a positive charge right after starting, then taper back down to 0. It may show significant discharge at idle with the lights on, that's normal and it'll top itself off once you start moving again. But it should be obviously keeping up with demand by showing a charge that tapers off as the battery is topped off while driving at speed. With the lights on, it should end up just above 0 when you're moving.

 

You can also test the output by putting a voltmeter on the battery while running at about 1000 RPM. It should show 6.5 to 7.5 volts, which would indicate that there's current moving into the battery. If it shows close to 6 volts or less, then there's no current coming out of the generator (or the regulator isn't energizing the field coils).

 

Is your battery connected properly? Buicks were negative ground in 1941.

 

Since the ammeter is showing a heavy discharge with the lights on, I'm going to assume it is working correctly and is properly connected.

 

Do a few more tests and let us know what you find. New regulators are usually available at NAPA or online (they're not 100% correct, but they work for drivers) and there's at least one very good generator rebuilder here on these forums if you can't find one locally. It's not expensive.

 

Keep us posted!

Edited by Matt Harwood (see edit history)
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21 minutes ago, Matt Harwood said:

You should determine whether it's the generator or the regulator that's faulty. Ground the field terminal on the generator (momentarily) and see if it goes to full charge on the ammeter. If so, the generator is OK and it's probably your regulator. If not, the generator likely needs to be repaired.

 

A healthy generator should pretty much keep everything at 0 once the battery is charged. It should show a positive charge right after starting, then taper back down to 0. It may show significant discharge at idle with the lights on, that's normal and it'll top itself off once you start moving again. But it should be obviously keeping up with demand by showing a charge that tapers off as the battery is topped off while driving at speed. With the lights on, it should end up just above 0 when you're moving.

 

You can also test the output by putting a voltmeter on the battery while running at about 1000 RPM. It should show 6.5 to 7.5 volts, which would indicate that there's current moving into the battery. If it shows close to 6 volts or less, then there's no current coming out of the generator (or the regulator isn't energizing the field coils).

 

Is your battery connected properly? Buicks were negative ground in 1941.

 

Since the ammeter is showing a heavy discharge with the lights on, I'm going to assume it is working correctly and is properly connected.

 

Do a few more tests and let us know what you find. New regulators are usually available at NAPA or online (they're not 100% correct, but they work for drivers) and there's at least one very good generator rebuilder here on these forums if you can't find one locally. It's not expensive.

 

Keep us posted!

Ok i will keep testing. My father is coming over with an Ammeter so we can go from there. Right now if i ground the field on the VR i see no increase in voltage at all. Making me believe its the generator, however we will follow the test you suggested and the ones in the service manual. I do have the battery properly connected. I will need some info on what VR i should buy and who should rebuild the generator because it def is one of the two.

 

Thanks

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Looks like generator is the issue. Did the tests and no charging even with the field to ground. Not sure why it burned up but my pops says it is because he changed the bronze bushing to sealed bearings and I continued to oil them without knowing and flooded the armature with oil. This is the possibility as of right now

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AFAIK on the 40-41 gens there is no sealed bearing available for the rear. It remains a bushing (X4242) and you have to do a procedure to open up the side of the bushing so the wick passes oil from the rear reservoir. I did this last year and did a writeup here:

Cheers,

Dave

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Starter? What? Unless the starter is dragging and remaining energized somehow, it won't have any effect on the charging rate. Your starter can be bad and the electrical system will still charge the battery

 

Did the generator put out current when you grounded the field terminal? Oil shouldn't have hurt anything--it would just run out the bottom of the case before collecting enough to cause damage. How much did you put in there? Did you take the cover off the regulator and see if the points are closing? There are literally two possible things here that are causing your lack of charging: the generator or the regulator. If the generator puts out current when you ground the field terminal (not at the regulator but on the generator itself), then it's working and you should replace the regulator. If it does nothing, then you should have the generator checked, as it is likely faulty. Not much else beyond that and certainly nothing to do with the starter.

 

You're not being very clear about what you're doing which makes it very hard to help.

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The starter I brought up because someone asked about the sealed bearings and I thought I put them in the generator but instead it was the starter, unrelated. 

 

I did not not get any charge by grounding the field. I did it differently though. I made a jumper from the Fied terminal on the VR to ground. Didn't have an ammeter so I couldnt tel if I got current but no increase in voltage at high idle so.... did I do this correctly?

should I had grounded the field at the generator leaving everything connected. I assume this is the same idea since the wire on the voltage regulator runs down to the generator.

 

OR, Should I be disconnecting the field off the VR and grounding that wire,not leaving it connected to the VR? 

It wasn't clear if I leave everything connected when grounding the field!

 

thanks

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I can't see where step #2 of the above procedure is necessary.     When I do this.... I do step #1  then start the engine and  "rev" it a bit .....if the dash ammeter shows good charge then I know the generator is good and it must be the regulator or wiring or connections or (?).    

 

Or course step #2 will help give you a more accurate determination but you need a good high capacity ammeter and the test takes longer..

 

I skip #2 and am satisfied with "good enough"

 

Have you checked to see if the base of the regulator is well grounded ?

 

Jack Worstell       jlwmaster@aol.com

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The reason to ground the F terminal of the generator instead of the F terminal of the voltage regulator is you want to test the generator, not the generator AND the wiring from the generator to the regulator at the same time. One part to test each step. IF the generator charges with the F generator terminal grounded, then the next step would be to ground the F terminal of the regulator to check the wiring of the field circuit.

 

Divide and conquer troubleshooting.

 

 

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After seeing the pictures and noticing that the wiring is all original, the problem could be the wiring. The original insulation is very brittle and there could be some exposed wires or wires touching each other in the harness.  Just some thing to think about.

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At this point, I'd FIRST disconnect the battery, then remove the generator and regulator (after photographing connections and tagging the wires) and take them to a generator rebuilder, preferably the one who rebuilt the gen awhile ago. I'd figure that I'd already spent too much time on an amateur diagnosis.

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Grounding the F terminal of the generator is not amateur diagnosis. It is in all the shop manuals of vehicles that use this system. I say that, because other systems need to have a hot wire applied to the F terminal. The shop manual will give the proper instruction.

 

Photographing wires is a great idea.

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For your information:  When you get the generator back from the rebuilder:  Instructions on how to polarize the generator.  This instruction sheet came in a NOS 4-terminal voltage regulator for cars when you converted the old 5-terminal VR to the new style 4-terminal VR.  I think the '41's use a larger generator and a different VR, but maybe the polarizing instructions are similar?

 

 

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Edited by Gary W (see edit history)
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Rebuilt generator and new voltage regulator. Hopefully many more years of good service. 

 

Question: are these good numbers , 7.5v idle and 8.3 if I rev it up.

 

i didn't adjust the VR, just put it in

6 volt battery, it won't boil my battery?

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1 hour ago, FLYER15015 said:

What is the "plastic" cover on the back of the Gen ?

I've not seen one of those before.

Is it year /  model  specific ?

An air scoop ?

 

Mike in Colorado

 Ok I will drive it around and see.

 

The piece on the back of the generator is a heat deflector which came with the compound carburtation cars. It's steel.  Mine does not have compound carbs but the generator has that piece so it must has been replaced.

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