Farmall Cub

So, just when I thought I had this figured out.....

My tractor is a 6v negative ground with a regulator and magneto ignition.
After looking at the various threads about wiring and trying the various setups in those threads.....

First, the tractor is not charging.
Second, with the lights on the dim setting the voltage drop resistor starts smoking.

I currently have it wired to be more of a cut out then a regulator.
In other words there is nothing connected to the "L" terminal on the regulator and I'm grabbing power from the ammeter for the light switch.
The "BAT" terminal on the Regulator is connected to the "+" side of the ammeter.
The "F" terminal is connected to "F" generator lead with the remaining generator lead attached to the terminal on the underside of the regulator.

Assuming you have checked the obvious things like the tightness of the generator belt and polarizing the generator, one thing that caught my attention was your setup with a negative ground. I believe voltage regulators are specifically designed for positive or negative ground systems, but not both. If the VR is designed for use on a positive ground system (and a lot of cubs are set up that way), it will burn out in a negative ground system (according to Delco). Also, if you have a magneto system, I don't believe you need the "L" terminal on the VR as long as there is a wire from the ammeter to the switch, which it sounds like you have.

Hi,

First make sure that your ammeter on the dash is working. Perhaps you are getting excessive current through the resistor and don't know it since the gauge isn't working.

With the tractor off and you turn on the lights is there a discharge on the ammeter? (I assume the meter would read a discharge, but you noted that it is negative ground so unless the wiring to the meter was changed I guess it could read a positive charge). Anyway, a deflection should indicate that the meter is functional.

Next, with the tractor running, check the generator with the motor test. From the generator ground out the F terminal. Make sure it is a good ground. Next run a wire from the A terminal to the battery. Positive in your case. The generator should run and should move the ammeter to indicate charging.

If these are good then most likely you need a new voltage regulator/cut out. There could also be bad connections somewhere in the mix, but the smoking resistor to me would indicate excessive load and not a bad ground.

Todd

Bill V makes good points. Remember to repolarize the generator before you test it.

Todd

Like Todd said the smoking resister could be excessive load, but it could also be that one side is hot and the other side is grounded or shorted out. You don't say if the lights work when they're turned on or if the tractor is running when the resister is smoking. Also is this a new problem that just appeared or had you done some work that may have created the problem?

Correction,,,,,,6v Positive ground.

Let me answer the questions I know as of now.

The lights do work as expected and the ammeter does show a discharge.
I took out the light bulbs and they are T1133, but have a 5A rating. Most of the 1133's I have seen on-line have a 2.5 - 3 amp rating.
This might be the source of the excessive draw. I'm going to try different bulbs as a next step.

With the tractor off, I removed belt and connected the generator to the battery and it turns....rather slowly, but it does turn so I think it's probably ok.

Todd,
I don't understand this test,
"Next, with the tractor running, check the generator with the motor test. From the generator ground out the F terminal. Make sure it is a good ground. Next run a wire from the A terminal to the battery. Positive in your case. The generator should run and should move the ammeter to indicate charging."
Can you please explain further?

Thanks

One more request,
I have seem several wiring diagrams on this site, all a bit different.
Does anyone have a diagram they KNOW works?
I have a generator with a (4) terminal regulator and a (4) position switch with the High/low discharge setting (it has the connection with the resistor for the F connection).

Thanks

You wont find a diagram like that. The 4 position light switch was designed for use with a cut out, not a VR. The smoking resistor is common with the lights on dim. It gets hot and there is usually some crud built up on it. You can try grounding the F terminal with the tractor running to see if it shows a charge on the meter. As previously noted, make sure it is a good clean ground. Also, again, make sure to polarize the generator.

The below link has two cub wiring diagrams. Since you have a voltage regulator instead of a cutout, the lower diagram is probably the closest match. If you have a VR controlling the charging circuit, the light switch controls only the lights. With regards to Todd's test recommendation, if you jumper the generator Field terminal to ground, the ammeter should indicate a charge. If it does you probably have a bad VR.

http://www.atis.net/CubFAQ/cub_faq_2.html#q3

Thanks for the diagrams Bill.
Those are the diagrams I have and my tractor seems to be a combination of the two.
I have the four position switch as shown in the first diagram and a regulator as shown in the second diagram.
I have a magneto ignition, so the battery is just for starting and running the lights.
Can I hook the regulator up like a cut out i.e. connect the "F" terminal on the generator directly to the switch, leave the "L" and "F" terminals on the regulator unconnected?
Will grounding the "F" terminal with the tractor running still show a charge in this scenario?

Thanks for all the help everyone!

Oh ya, the insulation material on the drop resistor is burning off when the lights are on dim.
The PO had the wiring really messed up, so I appreciate the help untangling it.
I might just go back to a cut out as designed and forget about monkeying around with the regulator.

In a similar vein. I'm not a wiring guru as some of you who have tried to help me know. I rewired the Cub a couple of weeks back and the only glitch i was aware of was I think I have the wires reversed on the ammeter. It would show discharge instead of charging when it should have been the other way around.

And I also noticed I messed up the four-way light switch but that seems minor. My backup light comes on and with the next click of the switch my front lights come on but I don't have the option of high or low beam. Everything seems advanced by one click. I probably pulled from the wrong terminal on the switch but it raised a question when I had the lights on today checking things over. With the tractor running, the ammeter shows a pretty good deflection when I have all three lights burning. Is that normal? I may have the wires reversed at the alternator, that's the only thing I can think of...discharging the battery. I guess a sure way to find out is a dead battery down the road.

I really don't want to take the hood off again quite so soon.

All cubs were factory 6 volt positive ground from the factory untill mid 64 when they went to 12 volt positive ground. Cubs from 47 to mid 49 had a cut out with 4 position switch to regulated the charge. If you have a early cub with 4 position switch there is a special regulator to replace the cut out. It will be a positive ground regulator. be ware that there are a bunch of foreign junk regulators out there as well and most other parts. I have had good luck with the Brillman co. they sell made in USA regualtors. are pricy but still cheaper than having to replace the taiwan junk.

vw:

Let me preface this by saying I am no guru -- I needed help. But at least that thread is still around - Generator and Cut-Out That may be of help to you.