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WD Electrical question

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dave Kolby

03-21-2000 13:29:18

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My 1948 WD (magneto ignition) indicates an electrical discharge when the light switch is in the lights on position (lights are on). It has the original 6V system and original lights. It functions correctly in low charge and high charge positions. I have the manuals but the wiring hookup is unclear in the drawings concerning how the charging circuit is hooked up in the headlights on position of the switch. Can anyone tell me what to check for here to correct this condition? I know it does not charge a lot when lights are on but it should not show a discharge either. Any help appreciated.

Dave

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Bob Semrau

03-23-2000 08:48:21

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Re: WD Electrical question in reply to dave Kolby, 03-21-2000 13:29:18

I think that the WD works the same as my G does for this switch. I had to figure this circuit out because my G didn't have a switch - the field terminal was grounded, always giving high charge.
The switch is really controlling 2 circuits. One is the lights. The other is the field current to the generator. There is a resistor in the switch that the field terminal is grounded through when in low charge. With the lights on or on high charge this resistor is shorted to ground, allowing max generator output.
It is possible that this resistor isn't being grounded in the lights on position.
On my G I replaced the switch with a DPDT center-off toggle switch and a 3 ohm 20W power resistor.

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Rick

03-22-2000 08:48:44

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Re: WD Electrical question in reply to dave Kolby, 03-21-2000 13:29:18

Most all will show a discharge with the lights on and the motor at low idle, step the rpm`s up should go to + side but not alot as it would with the lights off. This is normal

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Brian G.

03-22-2000 05:38:28

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Re: WD Electrical question in reply to dave Kolby, 03-21-2000 13:29:18

Since your generator is charging under no load conditions at both low & high settings, I would check the fan belt. If the belt is loose and/or "glazed", it could be slipping when a load is applied such as the headlights. This may sound too "elementary" but sometimes we overlook the obvious. I've never messed with the "third" brush but some generators do have that feature. A friend of mine told me he adjusted the voltage output on his Farmall W-4 by adjusting the "third" brush. I looked in the oldest "Motors" Auto Repair Manual I have ('46-'56) but the only generators they show have only two brushes. I assume having a regulator or a simple cutout (as your tractor has) has some bearing on which type of generator is used. I know there must be some older mechanic out there that is going to give us the straight scoop!? Good luck, Brian G.

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Rick

03-21-2000 21:18:54

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Re: WD Electrical question in reply to dave Kolby, 03-21-2000 13:29:18

Hope this helps.

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dave kolby

03-22-2000 11:42:01

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Re: Re: WD Electrical question in reply to Rick, 03-21-2000 21:18:54

Thanks for the diagram Rick. I have the manual already with that drawing. What I can't figure for certain is this. The drawing shows the three positions of the switch but does not show if there is a slider on that resistor which effects the generator charge rate. I assume that is how it works?? I too am hoping some older ex-AC/WD mechanic might set us straight on this. BTW as to the comment about showing "some" charge but not much with the lights on at high rpm. I can run her full throttle and it always show a discharge with the lights on, not even a center scale and no plus at all on the ammeter.

Dave

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Phil Auten

03-21-2000 13:50:36

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Re: WD Electrical question in reply to dave Kolby, 03-21-2000 13:29:18

Dave,
You may need to adjust the third brush (if your generator is the third brush type). The manual for my B describes the procedure sketchily, but it should be in your WD manual too, along with the schematic.

Phil

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dave Kolby

03-21-2000 16:12:36

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Re: Re: WD Electrical question in reply to Phil Auten, 03-21-2000 13:50:36

Thanks Phil,

I have all the AC manuals for the WD and there is no mention of set-up for a third brush or any mention of setting up the generator at all except for polarizing it. The schematics show connections from the voltage regulator on but nothing internal to the generator. I "suspect" there may be a resistor or some connection on or in the light/charging switch which is bad or hooked up wrong. It is apparently, as far as I can see, wired according to the book. There is no breakdown on what is in the circuit when the lights are on.

Dave

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Phil Auten

03-22-2000 05:34:35

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Re: Re: Re: WD Electrical question in reply to dave Kolby, 03-21-2000 16:12:36

Dave,
Sounds like the switch is bad or the wiring from the high charge terminal has a resistance in it (bad connection, broken strands, etc.) that is not allowing full current flow. I would see if the switch can be disassembled to check the contacts for burning or corrosion. If the switch is ok, I think I would check for hot spots in the wiring, indicating a bad spot. Replace whatever is getting hot to eliminate the resistance, and recover the lost charging current. Remember, you can't violate Ohm's Law. The higher the resistance, the lower the current at the same voltage.

Phil

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