Charging test not happening

Thu Feb 20, 2014 10:42 pm

I'm trying to test the charge on my '50 Cub that has been converted to 12V negative ground, but the muti-meter goes wild when I touch the probes to the terminals. I believe it's charging, but I'd like to be able to see what it's doing for sure. Any ideas what may be up?

The ground is currently connected to the battery box itself.

Re: Charging test not happening

Fri Feb 21, 2014 6:13 am

You need to use an analog meter , digital will not work. I'm guessing that is your measuring problem.

Berlin

Re: Charging test not happening

Fri Feb 21, 2014 8:13 am

Alright, I'll try that.

Thanks.

Re: Charging test not happening

Fri Feb 21, 2014 12:13 pm

Engine off for several hours. Test/read battery voltage across terminals.

Run engine for 5 or 10 minutes. Shut engine off. Test/read battery voltage.

Initial battery voltage reading should be 12.? volts. After running tractor for a few minutes, battery voltage will be higher than your initial reading if the 12 volt generator or alternator is functioning. If the 2nd test/reading is slightly lower than the initial test - not functioning.

You can do the checks with a digital multimeter.

Amp gauge or volt meter installed in tractor's dash?

Edit. Surface charge. If the battery voltage is higher immediately after running the tractor, the voltage reading will be almost the same as the generator/alternator output voltage. However, this will not tell you the amperage out put.

Re: Charging test not happening

Fri Feb 21, 2014 9:10 pm

You can surely check the charge of your new system with a digital meter.

For starters, take the top off of the battery compartment ( if you already haven't ).
Make sure your digital multimeter is set to DC volts
Press the black probe to the ground stud on your battery and the red probe to the positive stud. I'm guessing it will read 12.8V - 13.0V (high 12s)
Now crank your tractor. Rev the RPMs on up to get the alternator charging.
Now repeat the battery voltage test again. You should now be reading 13.6V - 14.0 V

You'll need a better meter to determine just how many amps the alternator is sending. Or an amp gauge, if one is still on your dash and is hooked up correctly.

Re: Charging test not happening

Fri Feb 21, 2014 9:37 pm

I believe all you have to do to set up the amp gauge correctly for a 12v is to just switch the wires right? Since ground is now negative?

Re: Charging test not happening

Fri Feb 21, 2014 9:47 pm

DieselDennis wrote:You can surely check the charge of your new system with a digital meter.
Original poster is saying his digital meter will not work on his 12 volt system. I own some high priced multimeters, Fluke and Klein, and they don't work on some 12 volt Cub systems.

I have purchased an analog multimeter for working on Cubs - and other tractors,

Re: Charging test not happening

Fri Feb 21, 2014 11:42 pm

I've been spinning wrenches for nearly 30 years, went on to trade school for it, and worked professionally as an ATV/cycle mechanic......but I've never had a voltage reading fluctuate from the bottom of the scale(set on 0-20. volt) to the top 50 times per second.

Just went out at 10:41 PM and checked voltage at terminals (engine OFF) and it's only showing 11.88-volts. With engine running, it's unreadable as described.

Re: Charging test not happening

Sat Feb 22, 2014 8:53 am

plowboysghost wrote:...but I've never had a voltage reading fluctuate from the bottom of the scale(set on 0-20. volt) to the top 50 times per second.
Just went out at 10:41 PM and checked voltage at terminals (engine OFF) and it's only showing 11.88-volts. With engine running, it's unreadable as described.


I had this happen on a 12 volt conversion on a H of my dads.
Double checked my work, then used a different meter.

Rodney 8)

Re: Charging test not happening

Sat Feb 22, 2014 10:43 am

Seeing a digital fluctuate connected directly to a generator is normal, both god ones and cheap ones. ON an alternator it is not normally that bad, but could be if the internal regulator is acting up, or if you have an older alternator that still uses slip rings and brushes. If you connect to the battery rather than the alternator, digital meters normally work normally. The only digital voltmeters

An analog voltmeter reads the voltage continuously, and the needle of the meter can only move at a limited speed, so it shows an average. A digital voltmeter samples (counts), several times a second, and shows that reading. At the generator or an old style or malfunctioning alternator there is a lot of electrical noise, consisting of voltage spikes, etc. and that really confuses a digital meter. If you connect to the battery instead, the length of the cable and the battery filter that noise and you get a more stable reading.

This sounds like a good opportunity for the next Cubfest I go to. I can bring both types of meters plus an oscilloscope to show the noise at a generator or alternator versus at the battery.

Re: Charging test not happening

Sat Feb 22, 2014 11:09 am

Update:

The short story is that the alternator bracket was broken, and the alternator belt loose under increased RPM. Got the bracket welded and like magic, I ended up with 13+ volts at half throttle. All of a sudden, my ammeter is working , too :)

Re: Charging test not happening

Sun Feb 23, 2014 6:28 am

plowboysghost wrote:I've been spinning wrenches for nearly 30 years, but I've never had a voltage reading fluctuate from the bottom of the scale(set on 0-20. volt) to the top 50 times per second.
When I was a bit younger, in the 1950's, you could tell the make of vehicle driving past the house because of ignition interference on the radio or TV. - - - Ford.

Manufacturers have added resistor spark plugs, shielded wires, capacitors, moved and added ground wires/locations, to reduce or contain EMF (electric and magnetic force) radiation.

When most Cubs were manufactured, EMF radiation from tractors was not a concern. Back then, farm tractors were not normally operated close enough to a house with a radio or TV. Providing the farm house was fortunate enough to have electricity and could afford a radio or TV.

Re: Charging test not happening

Sun Feb 23, 2014 6:29 am

plowboysghost wrote:I've been spinning wrenches for nearly 30 years, but I've never had a voltage reading fluctuate from the bottom of the scale(set on 0-20. volt) to the top 50 times per second.
When I was a bit younger, in the 1950's, you could tell the make of vehicle driving past the house because of ignition interference on the radio or TV. - - - Ford.

Manufacturers have added resistor spark plugs, shielded wires, capacitors, moved and added ground wires/locations, to reduce or contain EMF (electric and magnetic force) radiation.

When most Cubs were manufactured, EMF radiation from tractors was not a concern. Back then, farm tractors were not normally operated close enough to a house with a radio or TV. Providing the farm house was fortunate enough to have electricity and could afford a radio or TV.