jumpy alternator needle

Sun Nov 04, 2012 2:24 pm

Alternator needle started jumping back and forth between slight discharge, occasional charge, and needle straight up. Also, strangely, it now shows more charge when the lights are ON. A new battery was just put on but connection looks o.k. to me. It does seem like this happened years ago and jiggling some wires fixed it. What should I be checking ?

Re: jumpy alternator needle

Sun Nov 04, 2012 4:06 pm

What year is your cub and does it have a factory Alternator?

Re: jumpy alternator needle

Sun Nov 04, 2012 6:23 pm

Cub is a 1952 and does have factory alternator.

Re: jumpy alternator needle

Sun Nov 04, 2012 6:27 pm

dhart wrote:Cub is a 1952 and does have factory alternator.

Generators only back in that year so we'll need more info, should have been a 6 volt also.

Re: jumpy alternator needle

Sun Nov 04, 2012 6:53 pm

Alternator needle = question amp gauge? The description of the symptoms suggests the electrical system is a generator with a regulator and not an alternator.

What happens with the needle when the engine is operated at 3/4 full throttle?

Before we diagnose the problem we need to identify the electrical system. The operator's manual for the tractor shows a generator with either a cutout or a regulator. There are pictures of an alternator installed in a Cub on this site, search for "alternator installation".

Re: jumpy alternator needle

Sun Nov 04, 2012 7:13 pm

Alternators really are best with a volt meter and generators are best with an amp gauge. Which do you have?????

Re: jumpy alternator needle

Sun Nov 04, 2012 7:57 pm

Why should a generator be checked with a ammeter instead of a voltmeter? Is it because of the need to check while under a load? Most rebuilders check for volts while tweaking the VR to set the necessary charging rate.

Re: jumpy alternator needle

Mon Nov 05, 2012 8:17 am

As Yogie suggests, this is probably a situation where the charging system has been misidentified. For my part, I think it best to determine exactly what charging equipment is on that tractor and then offer suggestions that apply to that specific equipment.

For folks of age 50 and under, all the new on-road vehicles made in their lifetime have had alternators. Generators are, to many, those things you use at home or camping when there is no other source of electricity. But in actuality, those are alternators!

Re: jumpy alternator needle

Mon Nov 05, 2012 8:26 am

Following this post with a lot of interest.

I have an H with similar symptoms. It is 6 volt, positive ground, generator system. My suspicion (in my lack of knowledge :oops: ) is probably the voltage regulator.

I do not want to steal this thread, but any thoughts are much appreciated. :{_}: :{_}:

Re: jumpy alternator needle

Mon Nov 05, 2012 12:31 pm

Mr. E,
Regulators for the 6 volt generators can cause needle movements as the contacts make and break in the regulator. Such movements will be greater with a 20 amp ammeter than with a 60 amp meter since the variations are a greater percentage of the 20 than they are of the 60. Worn brushes in the generator can also cause that problem.

Re: jumpy alternator needle

Mon Nov 05, 2012 2:42 pm

On the matter of ammeters and voltmeters, using an ammeter with any Cub charging system, original or a conversion, requires the fewest revisions to the wiring harness. Using a voltmeter, especially with a magneto, requires more modifications/additions. Having both meters would be an attractive idea to me, but all of mine have just the ammeter. Except the newest non-IH tractor with the warning light only. On the ones where I have added flashing rear lights, the ammeter needle moves slightly in time with the flasher.

Re: jumpy alternator needle

Mon Nov 05, 2012 2:52 pm

O.K., Looks like my 52 CUB has generator with v. regulator.... it is a 6 V battery system and has a AMP gauge. It is also positive ground. Do you think it should be polarized since new battery? Have never had to before, but maybe should have. Thank you all.

Re: jumpy alternator needle

Mon Nov 05, 2012 3:09 pm

Sounds like a regular problem or a ground problem to me. I would tap the side of the regulator to see if it makes a difference. If so, you know where your problem is (either the contacts inside the regulator or the external connections to include ground). If you decide it is the regulator, buy a USA made one as the others do not seem to last long. --Lee

Re: jumpy alternator needle

Mon Nov 05, 2012 3:58 pm

dhart wrote:O.K., Looks like my 52 CUB has generator with v. regulator.... it is a 6 V battery system and has a AMP gauge. It is also positive ground. Do you think it should be polarized since new battery? Have never had to before, but maybe should have. Thank you all.

Not generally necessary but it is a good idea to polarize the generator any time the battery cable/cables are reconnected.

Re: jumpy alternator needle

Mon Nov 05, 2012 5:21 pm

I'd say if it's charging at all, it doesn't need polarization. Let's see what the consensus is...