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Farmall Cub Electrical

R

RandyM

Member
I've recently added a '54 Cub to keep the others in my barn
company. I have it running and thought of pushing some snow
with it just for fun. I intend to complete the rest of it in the
Spring as time allows.

I believe that everything was still original - wires, VR,
generator, etc. The generator was tested at the local auto
electric shop and is good. The battery is just over a year old
and is good.

When I start it, the D-O-C ameter pegs on full charge. If I set
the lights to dim, it shows a slight charge, and with lights on
bright it shows full discharge. The ignition switch was bad and
it was swapped for used one I had on the shelf. I've also
swapped out the 3-position light switch with one I had. This
did not change the charging indication. I've not yet put the
voltmeter on it to verify the charge in each condition.

I plan to rewire it and will likely install a new VR in the spring,
but for now, any thoughts on what might be causing the charge
to vary that much?
 
There are possible problems in the light circuit, as well as the regulator, and possibly the amp meter itself. If the tests were done with the engine at 3/4 throttle or so, the system needs to be checked for a short in the light circuit, or non stock light bulbs or lamp systems. The voltage across the battery terminals really tells the story. An amp meter with age can become inaccurate due to thinning of the internal shunt. Voltage should be 6.3 or a fraction higher when nothing is on, not running. at 3/4 throttle the voltage should be 7.1 to 7.4 volts. Jim
 
People have had enough trouble with new voltage regulators that I wouldn't be too cavalier about tossing an old one in favor of a new one. Diagnose and rewire as needed then troubleshoot any actual problems. The old regulator may only need contact points cleaned (DO NOT USE ABRASIVE PAPER OR CLOTH, JUST A FILE!).
 
Thank you both. My next step is to run it and check the voltage. I'll report back when I've been able to do that. I'm not really looking to replace the VR if it's not needed. The observations were at 3/4 to full throttle. I do have another amp meter (older) that I'll try. Thanks for the suggestion on the light circuit. That's now going into my troubleshooting steps.
 
Randy, if you want a method to determine if non charging is the fault of the Generator versus the Voltage Regulator, see Para 5 in my Troubleshooting Procedure for full fielding and by passing of the Voltage Regulator functions.

John T
John Ts Charging Troubleshooting
 
John, I have seen your procedures and used them other tractors finding them very helpful - they helped determine that my Farmall 230 regulator only needed a minor adjustment. I have a trusted auto electric shop within a couple of miles that bench tested the Cub generator and found it was fine. The fluctuation from high charge to low charge with a change of the light switch didn't make sense to me.
 
(quoted from post at 05:10:00 12/15/14) John, I have seen your procedures and used them other tractors finding them very helpful - they helped determine that my Farmall 230 regulator only needed a minor adjustment. I have a trusted auto electric shop within a couple of miles that bench tested the Cub generator and found it was fine. The fluctuation from high charge to low charge with a change of the light switch didn't make sense to me.
Click to expand...

Does it have a regulator on it or a CUT-OUT ? If it has a Cut-out then the light switch does control charging duties between high and low charge. An original light switch with 4 positions (Low-High-Dim-Bright) is needed in this case. Those old 6 volt systems work well when properly maintained and the correct parts used.
 
It has the voltage regulator and three position switch. I've
swapped the original light switch with another I had on hand. I
know I need to rewire which should resolve the problem. I was
just curious about the amp meter swing with the different switch positions.
 
Seems this is the amp meter. I've just checked it with the multimeter. These are across the battery:
No lights
Idle - 6.58V
Full - 7.14V

Lights on dim
Idle - 6.39V
Full - 6.63V

Lights on bright
Idle - 6.01V
Full - 6.06V
 
Do the same test with the field terminal on the Gen grounded with a jumper. It will not hurt anything, and will provide full gen output bypassing the regulator voltage section. If the voltage goes up with the lights on bright and dim. it is the regulator that could use adjustment. Jim
 
The ammeter swing is pretty simple:

Bright lights draw more current than dim lights. Your generator can't keep up with the demand.

You might have a dead short somewhere. If you wire the lights wrong you can end up feeding 12V directly to ground.
 
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