Electrical folks

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wesome
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Electrical folks

Postby wesome » Mon Sep 16, 2019 2:16 pm

Question for the guys that understand electrical systems. The previous owner of my '73 IH Cub converted from 6V to 12V. He didn't recall what the ground was and I can't figure it out. The neg battery cable goes to ground but the wire on the negative side of coil the goes to the distributor and I thought that was the case with a positive ground? If this is all bass-akwards, how much have I screwed up running it like this?

wesome
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Re: Electrical folks

Postby wesome » Mon Sep 16, 2019 2:18 pm

Oh, and the Ammeter is the original 6V 0-30 that doesn't move. My multimeter says just over 12 volts coming back to the battery when running

Jim Becker
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Re: Electrical folks

Postby Jim Becker » Mon Sep 16, 2019 2:34 pm

Harvester changed the Cubs to 12-volt in 1964. A negative ground system should have the negative terminal of the coil going to the distributor.

Eugene
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Re: Electrical folks

Postby Eugene » Mon Sep 16, 2019 2:52 pm

wesome wrote:Oh, and the Ammeter is the original 6V 0-30 that doesn't move. My multimeter says just over 12 volts coming back to the battery when running
Crank the engine over several times with out starting the engine. Pause for a minute or two, crank the engine over again with out starting. Check to see if you have dropped the battery voltage to slightly below 12V.

Start engine, run at 1/2 throttle. Check voltage across battery terminals. If above 12 volts and ammeter not moving, faulty ammeter. You would like to see approximately 13.5 volts with the alternator charging.
I have an excuse. CRS.

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Glen
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Re: Electrical folks

Postby Glen » Mon Sep 16, 2019 4:45 pm

Hi,
A 1973 Cub originally had a 12 volt, negative ground electrical system, like Jim said above.

Below is a page from the 1965 Cub and LoBoy owner's manual, with info at the lower part of the page.

http://farmallcub.com/rudi_cub/www.clea ... age-25.jpg

This page below says it is negative ground, below the battery pic.
The electrical system should look like in the pic in the upper part of the page. They originally had a generator. Someone might have changed it to an alternator.

http://farmallcub.com/rudi_cub/www.clea ... age-26.jpg

Below is the 1965 Cub and LoBoy owner's manual. The experts on here recommend people read it. It has lots of info about operation, maintenance, and lubrication.
There is a table of contents on page 1.
It shows how Cubs originally looked in it.
They have said on here that IH didn't make a new manual every year.
A 1973 Cub is almost the same as the manual shows, the ignition switch and starter switch are different.
The manual has 6 and 12 volt electrical system info. Disregard the 6 volt info.

http://farmallcub.com/rudi_cub/www.clea ... index.html

I would check or change all the oils before using the Cub. Using it with low oil in a gear case can damage the parts in it.
The lube section begins on page 59.

wesome
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Re: Electrical folks

Postby wesome » Mon Sep 16, 2019 6:08 pm

Thanks, Jim- that's great news.
Appreciate it, Eugene. I know the ammeter is bad because the needle stays at discharge (and with the same reading) no matter what I do. Engine on or off. I tried as you suggested and had 12.7V so at least not discharging.
Glen- I'll copy those, thanks. I did change oil right off.

I appreciate you guys! Sorry to keep coming up with problems.

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Re: Electrical folks

Postby John *.?-!.* cub owner » Mon Sep 16, 2019 8:39 pm

May not be that the ammeter is bad, it may be the power from the alternator does not go through it.
If you are not part of the solution,
you are part of the problem!!!

wesome
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Re: Electrical folks

Postby wesome » Tue Sep 17, 2019 3:06 pm

good point!

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Re: Electrical folks

Postby tst » Wed Sep 18, 2019 10:28 am

12.7 is not charging, that is just battery voltage, a fully charged battery with a working alternator should read 13.5 to 14.5 volts

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Re: Electrical folks

Postby halftonstude » Sun Sep 22, 2019 3:05 pm

a side note on the ammeter, it is not voltage sensitive. the same ammeter can be used on a 12v or a 6v system. Only time it matters if there is a backlight bulb inside... that bulb requires the proper voltage. our cubs don't have a bulb back there. Big ammeters are just a resistor that measures the voltage across it when current is flowing. it doesn't matter if it's on the ground side or the battery side. they're usually calibrated full scale with 25mV or 50mV. they'll work forward or backwards, they just need to be hooked up right to get you the information you need. Keeping the 6v ammeter with a 12v conversion will not affect anything. Current range should be minded though, you don't want to shove 100 amps through a 30a meter...
c


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