1948 Cub Voltage Regulator or Generator problem?

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Jimmymike
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1948 Cub Voltage Regulator or Generator problem?

Postby Jimmymike » Tue Mar 24, 2015 8:34 am

I have a new problem with the '48 Cub. When you first start the Cub the ammeter gauge shows a good charge, 30 amps and then starts to fall off. About a minute into the run the gauge starts to act erratically, moving very quickly from zero to charging, back and forth. Then it stops charging all together. Once you stop the tractor and then restart after sitting the same problem reoccurs. Also when the gauge starts to act up the tractor engine changes tone while running, not rough. I tightened the fan belts up, they were loose, and it did not have any affect on the charging. Could I have a short somewhere since it does slightly affect the running of the tractor at slow idle when the gauge shows erratic movement? Once you speed up the idle the gauge will go to zero and the tractor runs normal. How can I tell if it's the generator or voltage regulator acting up, or both? If I had a short wouldn't the gauge just go to zero or into the minus? I hate to just throw parts at the engine without trying to determine what's causing the problem. Can someone help me troubleshoot this new problem?

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John *.?-!.* cub owner
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Re: 1948 Cub Voltage Regulator or Generator problem?

Postby John *.?-!.* cub owner » Tue Mar 24, 2015 9:54 am

If you still have the original generator, one of the things wrong is the ammeter. The original generator was only capable of charging ay about 12 amps, not 30. Do you know what changes have been made to the wring and charging system over the years? A 48 would have originally had a cutout not a regulator, and you controlled the charge rate with the H, L settings of the light switch.

Discounting all the things I just posted about things not being as they were originally, your description indicates dirty contacts on one of the points in the regulator. Just a touch up wit a point file if you can find one, or a VERY fine file just lightly used on the internal contacts may do it.
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Jimmymike
Posts: 19
Joined: Thu Oct 30, 2014 7:32 am
Zip Code: 37380
Tractors Owned: 2007 John Deere 3203
1948 Farmall Cub
Location: Nickajack Lake, TN

Re: 1948 Cub Voltage Regulator or Generator problem?

Postby Jimmymike » Tue Mar 24, 2015 11:25 am

John *.?-!.* cub owner wrote:If you still have the original generator, one of the things wrong is the ammeter. The original generator was only capable of charging ay about 12 amps, not 30. Do you know what changes have been made to the wring and charging system over the years? A 48 would have originally had a cutout not a regulator, and you controlled the charge rate with the H, L settings of the light switch.

Discounting all the things I just posted about things not being as they were originally, your description indicates dirty contacts on one of the points in the regulator. Just a touch up wit a point file if you can find one, or a VERY fine file just lightly used on the internal contacts may do it.


Thanks John, I probably do have a cutout not a regulator. I haven't taken the hood off yet but I'm pretty sure what I can see now looks like the original setup based on picture comparison. I'm not at all familiar with this cutout, just like the magneto. That's why I go to you guys before I plunge head on into these things. The amp gauge may be bad, I can tell it's not the original one, too new looking. I thought 30 amps was a bit excessive. I will check out the internal contacts and see what happens.

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Re: 1948 Cub Voltage Regulator or Generator problem?

Postby staninlowerAL » Tue Mar 24, 2015 2:08 pm

Sounds like time to remove the hood/fuel tank for some maintenance. Don't forget to oil the fan shaft and mag, much easier to do with the hood removed. :lol: Stan

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Re: 1948 Cub Voltage Regulator or Generator problem?

Postby Stanton » Tue Mar 24, 2015 2:50 pm

Once hood is removed, you can tell a cutout by 3 connection lugs (BAT, F, & GEN) and/or by removing the top of the cutout cover to reveal only one coil; a regulator has two coils--if memory serves me correctly.

I had a bouncing ammeter needle until I replaced the dimmer resistance coil and field generator resistance coil behind my light switch. Works as it should now. Do the maintenance John recommended first before replacing anything.
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Re: 1948 Cub Voltage Regulator or Generator problem?

Postby BIGHOSS » Tue Mar 24, 2015 4:06 pm

When dealing with the problems that old tractors can present, two musts for your toolbox is a small cheap test light and a working analog V.O.M. meter. You do not have to be an electrician to be able to use them. The first thing to check for a charging problem is to take a reading across your battery terminals with the meter. Remember this reading (it should be either 6 or 12 volts). Start your engine and run it about 1/2 or 3/4 throttle. Take another reading with the meter. If no change, it is not charging. If charging, you will see a slight increase in voltage.
Test lights are ideal for checking if a switch or solenoid is working. If when activated you have current going into switch and none going out you probably have a bad switch. Don't want to bore everyone with more details, but simple tests are easy to make to determine if you have a bad switch or not. It keeps you from throwing unnecessary parts at it. JMHO.
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