Cub Cadet 123 Charging Problems

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Cub Cadet 123 Charging Problems

Postby ridgerunner97 » Sun Mar 04, 2012 5:38 pm

I just finished up putting new valves in my 123 and some other miscellaneous repairs. I had rebuilt the starter a month or so ago and put new brushes in it and cleaned everything out in the case it looked great inside aside from the bearings and brushes. Any ideas of where to start with my charging problem? I have no idea where to begin, I replaced the regulator/rectifier with a known good one and installed the wiring exactly as I had taken it off and i'm getting a dead battery, and the battery is also a relatively new battery that is good. Electrical is NOT my forte. Is there a way to make the K301 a self sustaining type engine? My brother's Wisconsin TR10 in his Bolens 1050 is electric start but will pull start and run without a battery...any help is appreciated gentleman! :beer:
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Re: Cub Cadet 123 Charging Problems

Postby Dave C » Sun Mar 04, 2012 9:58 pm

Courtesy of mr jim steel from the old registry site




1.) Confirm that the battery wire to the BAT terminal of the regulator is hot. It should be hot even if the key is off. Do not cross this wire with the blue GEN wire. If you do, the engine will try to crank.

2.) If that was not your problem, next remove the blue wire from both the starter/generator and the regulator. Check the wire for GOOD continuity. If OK, reattach at both ends.

3.) Now do the same with the yellow wire as you did with the blue wire. If OK, reattach both ends at the starter/generator and the regulator.

4.) Start the engine and run it at 3,600 rpm. Using a jumper wire or a screwdriver, temporarily ground the F terminal of the start/generator to its case or the frame. The unit should charge at this point, and you should hear a definite drop in rpm when the F terminal is grounded. That means the unit is charging, but it is an UNREGULATED CHARGE. NEVER LEAVE A MACHINE HOOKED UP THIS WAY. The unregulated charge will blow the battery up. Provided that you have already carefully checked the continuity of the blue and the yellow wires, and both are OK, then:

a.) If the unit does NOT charge when the F terminal is grounded (no drop in rpm), the starter/generator is bad.

b.) If it DOES charge (rpm drops), the regulator is at fault.

5.) Quick troubleshooting tip: You can use a screwdriver to ground the F terminal as the first step on any non-charging unit to quickly narrow down the trouble source.


BASIC OPERATION OF THE SYSTEM: Current is supplied to the key switch by a green wire. When the switch is on, current is shunted to the rectifier-regulator center terminal through a gray wire to turn on the solid state electronics. The rectifier-regulator is grounded through its mounting bolts. When the engine is running, AC current is generated in the stator under the flywheel and supplied to the outer two terminals of the rectifier-regulator. The diodes in the rectifier-regulator change this AC current into DC and the circuitry keeps it in check at about 14.5 VDC. The current is delivered to the tractor via the gray center wire.



1.) Check with a voltmeter set to 12 VDC to be sure current is delivered to the key switch through the green wire by placing one lead on the terminal and grounding the other to the tractor frame. It should always be present, whether the switch is on or off. At this time, check the key switch connection spades and terminals to be sure all are clean and intact.

2.) Turn the key switch on and check for current from the gray wire at its rectifier-regulator end to a ground on the engine.

3.) If you get no voltage, check the ground wire running from the engine cradle to the frame in the front right side area for good connections. Try for voltage between the gray wire and the engine block again.

4.) If you still get no voltage, but have voltage at the key switch green wire, either the switch, switch connections, engine to tractor wiring connector and/or the gray wire is bad.

a.) Check the engine to tractor wiring connector for grease/dirt buildup and for continuity and good contact between the spade and receiver ends.

b.) If you still get no reading, check the voltage from the key switch gray wire terminal to ground with the switch ON. If you DO get a reading, the gray wire is bad. If you DON'T, the switch is bad.

5.) If all is OK and you DO get a reading at the gray wire where it connects to the rectifier-regulator with the key switch ON, then take a voltmeter and set it to AC volts. Unplug the rectifier-regulator and start the engine. At 3,600 rpm, measure the AC voltage across the two white wires coming from the stator to the rectifier-regulator. Stator output here should be 28 VAC or more. If so, stator is OK.

6.) You have narrowed the problem to the regulator. Check the regulator mount bolts for good ground and firm attachment. The regulator must have good ground through these bolts to work.

8.) If OK, then the rectifier-regulator likely needs to be replaced.

©2002 Jim Steele

Used with permission.
Trying to save cubs... one at a time.......
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Re: Cub Cadet 123 Charging Problems

Postby D Nafziger » Mon Mar 05, 2012 6:27 am

My dad purchased a 123 new in 1967, it had electrical problems from new until I restored it a couple years ago. Along with that comment, I worked in these when the were new and we had problems with nearly every 123. On dads restoration I did the following: new wiring harness, new regulator, new ket switch, new ammeter, rebuilt the starter-gen, other words anything electrical was replaced. Fixed it but was $$$$.
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