Generator Questions

LeroyM

LeroyM

Senior Member
I need a step by step on how to polarize a generator from positive ground to negative ground.

Also who rebuilds Model A generators with a fairly fast turn around?
 
Simple method--with battery changed to new polarity-jump cutout with short wire for 2 seconds.

If you have diode cutout it needs to be changed for polarity, the electro mechanical cutout doesn't care about polarity, but anything electronic will.
 
I would first check to see if the generator would motor. Remove the Fun projects regulator for this and any other tests. Remove the fan belt and touch a hot wire to the post that comes out of the generator. If the generator begins to turn like an electric motor and is turning in the correct direction it is probably OK. If not or it motors in the wrong direction you probably made some mistakes when you installed the field coils . if the generator motors backwards you have the wrong wire grounded that comes off the field coils. If it passed the test, put the old cut out back on and hook the wire back to the cut out. To polarize , without the engine running touch a wire from one post to the other of the cut out for a couple of seconds as Tom Wesenberg said and the generator will be polarized and this won't hurt the old cut out. I know what I am talking about because I have ran 12 volts with a reproduction cut out, the only thing is with a cut out you won't have voltage regulation. If you jumped a wire across the posts of the Fun projects regulator you have probably killed it.

Actually you DON'T need the 12 volt field coils to run 12 volt. This was told to me by John Regan himself. The main difference in the field coils is, the 12 volt coils have smaller but more wire. I believe that larger wire is better. and the 12 volt field coils are more difficult to install because more wire is harder to squeeze down so that the armature doesn't hit the sole plates.

As far as the wiring I used the original wireing harnesses. The model As that I run with mallory dual point distributors , I run a wire from the distributor to the ignition switch just as you would with a repro switch and cable. You can look at the wiring diagrams in Brattons catalog and the only changes you will need to run negative ground is reverse the connections on the battery, coil and the ammeter. I think that most if not all the repro ammeters are model T and are negative ground. If it doesn't show a charge try reverseing the wires on the ammeter. You can hook the electric fuel pump to the ignition switch or you could just run a hot wire with a toggle switch between the wire and the pump.

I have been running the Fun projects regulator, 12 volt positive ground for four years with NO problems. I hope this will help.
 
If you have or think you might have a voltage regulator by Fun Projects (the regulator is inside the cutout and has no special markings on outside) then do not flash the generator, doing so will destroy the regulator.

Quote from the Fun Projects instruction sheet:

"Never short the voltage regulator terminals together​
​
as with a jumper wire to test the operation of the regulator or to flash the generator - The voltage regulator will be damaged. Remove the voltage regulator from the generator before performing any tests on the generator."​

 
I took the generator off. It does not motor or turn. I'm trying to figure out what is shorting out.
 
Did the generator charge before you installed the 12 volt field coils? You may have problems with some of the brush holder insulators or washers or maybe the armature is bad. I rebuild my generators and always check the armatures with a growler. you may need to polish the commutator and under cut the mica between the segments. Other than the field coils this is about all that comes to mind that would keep the generator from charging.
 
I got the generator turning! I went back out and took it apart. I had it wired wrong inside and also a short. The armature was tested months ago and was fine. Now if I put a old cutout on it and polarize it then it should charge correct?

I sent the voltage regulator back to have that tested so I can't try that at the moment.

Is it worth changing back to 6 volt field coils or just try it like it is once I get the voltage regulator back?
 
Purdy Swoft said:
Actually you DON'T need the 12 volt field coils to run 12 volt. This was told to me by John Regan himself. The main difference in the field coils is, the 12 volt coils have smaller but more wire. I believe that larger wire is better. and the 12 volt field coils are more difficult to install because more wire is harder to squeeze down so that the armature doesn't hit the sole plates.
Click to expand...

Yes, the genny will work with either field, BUT the minimum running RPM to get above battery voltage for charging will be higher. The field magnetic strength is a function of both applied amperage and number of turns of wire. The actual generator output in a Model A is from the armature, not the field coils. How heavy the field wire is has no effect on heat dissipation from the armature, the limiting factor in amperage rating.

I did plenty of generators, all kinds, in the early 60's on a Sun test bench and you can graph RPM vs output. I no longer have the spec cards, but one of the tests was to reach the regulator (cutout) relay switch point at a given low RPM (usually 1000 gen rpm). Using a field designed for 6V in a 12V gen app. will raise that rpm curve, giving poor low speed charging performance. I would definitely switch fields for an A that does more stop/ start putting around than highway running.
 
If the generator will motor in the correct direction I would put the cutout on and polarize the generator. I f the generator charges I would run it until you get the Fun projects regulator back. I had bought the 12V field coils but didn't use them because John Regan said to use the six volt coils. Mine works good and with the 12 volt reserve my lights don't dim at idle. If the 12V coils work ok I would use them. Good luck.
 
I would like to add. While you have the cut out hooked up set the third brush for a maximum charge of eight amps and not over 10 amps. If the generator surges as if the third brush is set for TOO high of a charge rate or if you have a loose battery cable it will damage the Fun projects regulator.

I didn't notice any difference in the rpm that the generator begins to charge when using the 6V field coils on 12 V than it did with 6 v field coils and a 6 V battery. I can't say how it will work with the 12 V field coils because after John said they were not needed, I didn't use them.

I use and recommend the generator cooler band with any model A generator for longer life. I also use the halogen head light bulbs from Australia, they are said to only draw 3 amps. I use the Pertronix flame thrower 40.000 volt 3 ohm epoxy filled coil. This coil has a built in resistor and I think it beats electronic ignition and only cost around forty dollars.
 
I didn't pay attention to which way it was turning because I got excited after finally getting it to work. I will try it tomorrow and see if it will charge with a cutout. Just for reference which way should it be turning?
 
The generator needs to rotate in the direction that the engine turns when it is cranked or when it runs. If it doesn't the generator will NOT charge. If the generator motors backwards the wires that come off the field coils are reversed as in the wrong wire grounded. I would be sure and check this before starting the engine. It can't be good to try and make it charge if the fields are hooked up backwards and it is an easy mistake to make .
 
I went out this morning and tried the generator to see which way it turns. It turns backwards. I tried changing the wires inside that go to the 3rd brush to see if I could get it to turn the other way but when I do that it doesn't turn at all. I'm following the diagram in Snyder's magazine for the generator.

Does anyone have a more detailed and up close diagram of the end plate that shows how its wired up to the brushes?
 
I went back out again and gave it another shot. The book calls for one of the field coil wires to go to the terminal bolt as a ground. Well some way or another it wasn't grounding with that bolt. I moved that wire to the ground brush that grounds to the end plate on the back and bolted it up. It now turns the same way the motor does.

I installed it back on the car but I can't get it to charge though. I haven't adjusted the 3rd brush yet and I don't trust the old cutout that I have. I'm going to order a solid state cutout from Snyder's for negative ground and try that some time this week.

If it's turning on the bench the same way the motor turns then it should charge correct?
 
Ok, one of the wires that comes off the field coils will hook to the third or adjustable brush the other wire that comes off the other field coil will ground to the case. if these wires are reversed the generator will motor backwards and will not charge. Hope this will help.
 
That's what was happening. It was turning but the wrong way. Some how another it was not grounding under that terminal bolt like it should. When I took the field wire to the screw on the back plate for ground it now turns the correct way like it should.

I'm going to mess around with the 3rd brush and see if that does anything with the charging. If not I know my cutout is screwed up and I'll have to wait until I get another one or the voltage regulator.

Thanks for the help.
 
I guess I should add. If the wire that connects the terminal post to the insulated brush is reversed with the wire that hooks to the adjustable brush, the generator will probably still motor in the correct direction and barely charge. If these wires are reversed , moving the adjustable brush will not increase or change the rate of charge. If run in this condition for very long the feild coils will be ruined, Be careful all wire connections needs to be tight and correct

The reproduction cutouts are mostly junk, about like the repro brake light switches. I have had the points to stick on them right out of the box. I have used them only when I had to. I have used them on twelve volts with as good of results as with six wolts. The repro cutout is the best to use for polarizing your generator and setting the chargeing rate BEFORE installing the Fun projects regulator. I can see no reason that the repro cutout wouldn't get you by for a few days if you keep a close watch on it. If it sticks a couple of taps on the cover with the handle of a screwdriver will unstick it. if you have a battery disconect switch I would use it every time that I wasn't running it or disconnect a battery cable. I 'm not sure about the diode conversions but If I bought one I would ask questions and make sure that it would work with 12V negative ground. I think I would get it working with the cut out and wait for your Fun Projects voltage regulator.
 
I heard back from Fun Projects on my voltage regulator. They said that my voltage regulator was working as it should. They also said that before putting the voltage regulator on that I should set the main brush "lead" on the generator, this is also called setting the main brush to "neutral".

Has anybody heard of this and if so how do you set the "lead" on the main brush or set the main brush to "neutral"?
 
For a stock cutout only: Momentarily short the wire that connects to the cutout to the generator output terminal to polarize the field windings. You can use the handles from a pair of pliers to connect the two terminals. Just flash it no need to hold them on the contacts. Do this while the car is running. This method was desribed in the Model T service bulletins. You won't get a shock.
 
Its good that the regulator is not damaged. I have never heard referance to main brush lead or setting main brush to neutral. John is an engineer and he uses different termanoligy than some model A home mechanics like me. I am pretty sure that he is refering to Third brush adjustment and correct wire connections inside the generator.

I will try again to walk you through the various processes. I will start with the brushes. The ground brush is the brush that grounds to the rear generator brush plate on the side next to the engine If the ground brush is grounded and in good condition you don't have to worry with it as no other wires hook to it. The next brush is the adjustable third brush . The field coil wire, number 2 in the exploded diagram in the new Snyders catalog on page A-137 attaches under brush screw number 50 on the adjustable brush. The next brush is the insulated brush that is sort of at the bottom of the rear brush plate. The wire that comes off the generator post, number 60 attaches under the insulated brush screw number 47. The other wire that comes off the field coils is grounded. In most model A generators this wire grounds under the generator post or terminal bolt number 61 against the housing or if you have a 1933 or34 model 46 generator that was used on the 4 cylinder engines, this wire will ground under one of the ears of the cutout number 59 or you can drill and tap a hole somewhere in the rear of the generator case to ground this wire or possibly under the ground brush wire. the main concern about the field ground wire is to be careful not to let this wire get against the armature so as not to rub through and short out. This covers the internal wire connections. To adjust the third brush you will need to push down toward the floor on number 41 the third or adjustable brush plate assy. . Pushing down on the third adjustable brush increases charge rate, pulling up decreases the charge rate. I have said it before but while we are talking about the setup you need to get the generator working first with the cutout before installing the Fun regulator. First polarize by touching a wire from one terminal to the other of the cutout for 2 seconds and you DON"T need to start the engine to polarize. After you polarize the generator if you have followed my rambling the generator WILL CHARGE. The next step is to set the third brush for an 8 and not over 10 amp charge and NO more. you don't want the generator to surge or it will ruin the Fun regulator. Also make sure that the battery cables are TIGHT or the generator can spike 40 volts and this will kill the regulator grave yard dead, believe me, I once assed around and made this mistake. After you get the generator working properly with the cut out you can Then install the regulator.and hopefully the real fun can begin. I will continue to watch and try to help any way that I can. Good luck.
 
You must log in or register to reply here.
Back
Top