Electrical problem

[Eugene]

Checked for volyage drop per Eugene.
Meter jumped all over the place from zero to 6 while cranking.

You need an analog (needle) multimeter when working on cub's electrical. Digital meters are effected by the ignition and generator EMF.

If engine cranks over well, not the battery.

[inairam]

Here's where I am.

Amp flow is 0.1

Should be 0.

Maybe something in the regulator/cut-off relay

The light switch allows the operator to do a high charge just after you start and to move it to low charge after a while. But you have to also remember to turn it off. This is if you have a cutout relay.

I have 1949 with a mag that has a regulator. I do not have to do that. The regulator takes care of it. So my light switch only controls the lights

[Jim Becker]

If I don't start it every couple days, the battery goes dead.

Amp flow is 0.1
. . .
Where should the light switch be set?
It was on "B".

If you have a battery in good condition, it will produce about 50 to 55 Amp hours of energy. If you are leaking off 0.1 amps for 2 days, You burn off 0.1x2x24 or about 5 Ah. That is about 10% of the charge. You probably wouldn't notice that when starting. You don't specify how many days it has to sit before it won't start, but if it is 2 weeks you burn off 0.1x24x14 or about 34 Ah. That is about 2/3 of the charge. Yes, you are likely to have trouble starting with that little of a charge. So the 0.1 Amp leakage matters.

You need to set your meter up again for measuring the leakage. It doesn't matter whether you measure it by voltage like I said or by amperage like Eugene said. Then you need to disconnect portions of the electrical system until the leakage goes away. If your connections at the switches and ammeter have not been cleaned up, I would probably start by cleaning those areas. The accumulations of corrosion, oil, dirt, grit, chaff, grass clippings, etc. that usually cover them can be part of the problem.

Do you not have working lights on the tractor? "B" is lights on at full intensity. Do you leave the switch on B all the time or did you set it there when you took the measurements?

[larryfoster]

Thanks for that info, Jim.
I'll start seeing if I can start eliminating things.

All lights are disconnected.
I noticed, today, that the light switch was set to the far right.
I'm kind of rusted there and the letter is blurry.
Can't remember where it's supposed to be or if it matters with the lights disconnected.

I did not moce the light switch to take measurements.

[Glen]

Hi,
I don't think you said if the Cub has a magneto, which a 1949 Cub came with, or a Battery Ignition unit.
The coil on the magneto wouldn't use battery power, if it is using the original style coil under the cover on top of the magneto, a Battery Ignition unit would use battery power.
If the Cub has no lights, I would use the first 2 positions of the 4 position switch.
The 1st position is Low charge.
The 2nd position is High charge.

[larryfoster]

Hi, Glen.
The Cub has a generator (battery ignition unit)
Thanks for the info.

[larryfoster]

After several days with the positive battery terminal disconnected, that the tractor started easily after re-connecting.
The ammeter showed charging and the battery was still at 6.37 volts.
I did notice the ground cable was loose where it connected to the battery box and tightened it.
Could that have caused my voltage draw?

To hunt for the draw, with the ignition button off, would I go to the next connection and see if there is any voltage?
For example, the starter is next.
Then the regulator, then generator, etc.?

Once again, thank you for your patience with this dummy.

Edited to add:
Disconnected ground cable from positive battery terminal and measured 15 milliamps.

[larryfoster]

A neighbor's son who works for a real good auto electric shop stopped by to fix my riding mower.
I asked him to look at my tractor.
After checking a few things, he pulled the fuse and the voltage draw went away.
Everything works with the fuse removed so I'm leaving it out.

I would like to find the problem so I'm not doing a workaround.

[Eugene]

I would like to find the problem so I'm not doing a workaround.

Wiring diagram for your tractor.

Only thing beyond the fuse is the lights. Same procedure as utilized before. Inspect the wiring for shorts. Disconnect one light at a time until you get zero volts. That light will be the problem - probably corrosion.

[larryfoster]

Thanks, Eugene.
What baffles me is the lights are disconnected and the wires are tied up.
But I may need to investigate a little bit

[Jim Becker]

I think in this case you are narrowing in on a light switch that is internally in bad shape. You could be leaking power through corrosion inside the switch from the input lug to the switch housing (which is grounded). You might try this test:
1 Stick the fuse back in.
2 Verify the leak is back.
3 Physically remove the switch from the tank support, leaving the wires attached and positioning the switch out of contact from anything except the wires. (remove screw from knob, remove knob, remove hex nut and star washer)
4 See if the leak goes away.
If the leak goes away, your problem is inside the switch. Some people have managed to take those switches apart and clean them up. I'm not going to advise down that path.

[larryfoster]

Thanks, Jim.
I'll give that a try.

[Glen]

Hi,
The fuse on the 4 position switch is originally for the lights.

I think in the past someone posted pics of inside the 4 or 3 position switch, I'm not sure which switch it was. The 3 position switch was used beginning during 1950 on Cubs, with the voltage regulator charging system.
There are one or more small springs inside the switch.
Be careful when taking one of them apart, that parts don't get lost.
I have seen new 4 position switches for sale online, that looked about the same as the originals.
I don't know how good they work.

[Gary Dotson]

You say your lights are not connected, do you plan to connect them any time soon? If not, why worry about it? I’ve opened up several of those switches and cleaned them up, just be careful when removing the back portion. If the switch is in fact the cause of your draw, you have nothing to lose trying to repair it.

[Bill V in Md]

Below link is the post Glen referred to regarding photos of the light switch:

https://www.farmallcub.com/phpBB2/viewtopic.php?f=1&t=28534&p=224279&hilit=Light+switch#p224279