6 volt or 12 volt generator ?

[bedfordboys24523]

I put a wiring harness in my 35 from mac's. I did not have any wiring in the truck before. It is wired to there diagram as well as vanpelts and others. The cutout seems to be working as it should opens at idle closes when rpm's increase. But when I hooked up the wire to the out put on the cutout and the contacts closed I got a bunch sparks and the amp gauge went backward's. So I checked volts coming out of the cutout and had 12v. My father sent me another gen in the mail, put it on today and its got 12v. I think I've got two 12v gens that might be neg ground as well. I guess my question would be how do you tell a 6v from a 12v and if it's a pos or neg ground?

[G.M.]

If it's a 35 generator with 3 brushes and a cutout on top. The third brush is on the lower side of the drivers side at the rear side of the generator under the metal band. Remove the band and slide the brush up. Up lowers the voltage and down increases it. With the engine running at 25 MPH engine speed with a fully charged battery turn the head lights on and adjust the brush so the amp gauge is about 1/16th inch about the "0" or just into the charge area. If you drive at night a lot set it up to 5 or 6 amps. If it's to high and you do mostly daylight driving it will over charge the battery. If it's a lead acid battery it will spit small drops of acid on the battery box and surounding areas. G.M.

[Brian]

Sounds like your wire could be contacting the frame of the cutout which is grounded. The screw needs an insulating washer or similar,so it connects the post from the cut out and the wire, without touching any other part.

[bedfordboys24523]

Its a 35 3 brush, Ive got the cover off the cutout I am using the plastic spacers on the screws so I know they are not touching any of the guts of the cutout. Is there a way of telling a 6v from a 12v when your at a swap meet. I seem to have two that have been converted to 12v. How many volts will a 6v gen with the 3rd brush increased all the way put out?

[G.M.]

It could put out in the range of 12 volts with no load, I doubt they are 12 volt generators. Push the brush all the way UP and see what you get. G.M.

[Karl Wolf]

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6V generator uses the cut out as a one way valve, so it should not allow electricity back thru the gen when not running... The battery controls the output voltage...

Hook up the gen cut out to the system, should not spark... Start the car, check the voltage... 3 brush takes a while to bring the battery up, so be patient... Adjusting the 3rd brush needs to be done after the car has run a while, adjustments are not felt imediatly... AND, mark where thing were before you start doing anything...
Karl

[Brian]

Where were the 'bunch of sparks' eminating from? You've got a major short somewhere as evidenced by the amp gauge going backwards. Try disconnecting both wires at cutout, and with the engine running at a reasonable rate, that in normal circumstances would allow the generator to charge, touch both wires together; [you may need a short extra bit of wire to accomplish this], and the ammeter should show a charge [and there should be no sparks]. If this works, it would indicate that there is a problem within the cutout, because all you've done is bypassed it. Disconnect the two wires before killing the engine to prevent the generator from 'motoring'.

[Flat Ernie]

As for positive/negative ground - did you flash the field coils prior to doing all of this?

Is this a real cut-out, or one of the aftermarket solid-state ones?

I prefer two-brush generators (even Harley used 3-brush generators early on & I swap those out too), but it's a preference.

[G.M.]

You don't have a solid state cutout. It wouldn't cut in and out as you described, it would go way down in voltage as the RPMs dropped. A diode doesn't cut out it lets current flow in 1 dirrection and blocks it in the other. A shorted diode would let current flow in both dirrections like a cutout with stuck points. G.M.

[Jerry Parr WI]

The 3 brush generator relies on the battery to limit the voltage. Without a battery the generator voltage will climb until it arcs internally and burns out. A 6 volt generator can be used to charge a 12 battery. The voltmeter tells the polarity. If it's incorrect just repolarize the gen. Great thing about these generators is they can be used for either voltage and either polarity.

[bedfordboys24523]

Thanks for the info I'm going out to the truck now to bypass the cutout and adjust the 3rd brush. Ill be back.

[G.M.]

You don't want to bypass the cutout with the engine not running at a pretty fast Idle. G.M.

[bedfordboys24523]

Ok im back with better news (I think). I disconnected the arm and batt wires that are on the cut out. Put a toggle switch and jumper wires to connect them, put volt meter on batt. Started truck and increased rpm's slightly, flipped toggle switch and amp's climbed to about 3, and batt went from 6 to 6.24 volts, and no sparks from anywhere! Is my cutout the problem, I attached a pic of the cutout(I hope). This is my first Flat v8 and it has been a learning process for sure. What cutout should I buy to deal with this issue?

[Karl Wolf]

DON"T by pass the cut out, you'll be buying a new generator...

Don't try to polerize a three brush gen, they don't.

Karl

[G.M.]

If you have a DC variable voltage supply you can clean the contacts and adjust where the cut out pulls in. Put the power supply to the body and the generator connection. Bring the voltage up slowly and with a voltmeter see where the contacts close. A 6 bulb volt across the ground and and battey connection will show you exactly when it closes. 6.8 to 6.9 would be good. You change where it closes by increasing or decreasing the spring tention. Clean the bottom edges where you ground the spot welds to get the cover off and solder useing an acid flux. G.M.

[31chevy]

You can install a diode kit from mac's # a10155d10 for $ 2.90 that will cure your cutout problem. I installed one on my 34 & it was rather easy & your cutout will still look original.
Gary.