Farmall Cub

Fellas,

Before I send my generator out to be rebuilt I'd like to confirm something with everyone. Using the testing flowchart to determine whether the cause is the generator or voltage regulator, I jumped the A term (generator term on regulator) to my Batt term on the voltage regulator. I immediately notice my ammeter jump to discharge (-8) and my battery dies.

As a second part to the test, if I jump my F term to ground I get no reading whatsoever on my ammeter which, according to the flow chart means a problem with the generator.

Any suggestions at this point? What does the negative ammeter reading when jumping Gen to Batt?

thanks.

Scotty, the jumper from the Batt terminal to the Gen terminal to polarize the generator is supposed to only be a momentary contact. A negative deflection of the ammeter would be normal during the momentary contact.
Are you saying that from the point in time that you performed the procedure, the ammeter stayed negative and drained the battery? Or did you leave this connection for a period of time?

If the generator does not charge with the field grounded, either it is defective or there is a poor ground connection through the generator mounts.

BigDog,

I guess I'm a little confused. I undertand that to polarize the generator, you should momentarily jump the Batt and A terminals however, the A term is also connected to the Voltage Regulator Gen terminal. As the flow chart suggests, I'm supposed to jump the Batt and Gen terminals together. Should I then first disconnect the A term from the Gen term before I do this? I left them together which resulted in a negative ammeter reading so all of that makes sense now.

As far as the F term goes, I get no reading on the ammeter when I ground that terminal. However I ran a continuity check from F to ground and it tested fine. So, shouldn't this mean that the generator ground is ok?

Thanks for your help.

Scotty, I sounds like your polarization procedure was correct. Did you notice a slight spark when you touched the 2 terminals with the jumper?
It also sounds like the generator ground is OK.
Now, if you have a voltmeter, take a reading from the A terminal of the generator to ground with the engine both stopped and running at half to three quarters throttle. Take the same set of readings across the battery terminals. If the voltage does not increase with the engine running, the generator is not working. If the voltage increases at the generator but not at the battery, you have either corroded connections or defective battery cables.

Bigdog,

I took a voltage reading across the A term to ground, F term to ground and across the battery. No voltage (or maybe 0.5 volts across A), no reading on F and across the battery reads whatever the battery started at with the engine off. I'd agree and say the generator's pretty much dead at this point. The only other thing I was going to try was to watch the cutout to see if it closes when the engine ramps up and then manually close it if it doesn't do it by itself. This should have been simulated during my jumpered tests however.

Thanks for you help.

You are correct, grounding the field manually removes the cut-out from the circuit. No voltage output from the A terminal indicates a non-functioning generator.