Generator won't stay polarized.
Generator won't stay polarized.
Over the last few years the electrical system on my 420 has been completely gone through, and it runs perfectly, except for one thing. Every time I start it, the generator will not charge until I fetch my piece of wire and touch it between the starter post and armature post on the generator. Even then it sometimes does not want to charge. I have even seen it start charging at a low rate, then when I rev the engine the meter swings over to DISCHARGE.
It used to work well. The regulator was adjusted to charge at 6.75 volts, that was less than 2 years ago.
My dad said to put a condenser on the armature wire, and I've thought of putting a button in one of the unused holes in the top of the instrument panel that connects the A terminal at the regulator to the BAT terminal on the switch when pressed. But those would just be band-aid fixes.
It used to work well. The regulator was adjusted to charge at 6.75 volts, that was less than 2 years ago.
My dad said to put a condenser on the armature wire, and I've thought of putting a button in one of the unused holes in the top of the instrument panel that connects the A terminal at the regulator to the BAT terminal on the switch when pressed. But those would just be band-aid fixes.
- JD440ICD2006
- 350 crawler
- Posts: 1113
- Joined: Tue Aug 22, 2006 3:57 pm
- Location: South Carolina
When it was completely gone through, was the generator completely rebuilt? There are $10 "kits" out there that only replace the brushes, shaft end bushing, and bearing. This is great as long as the coils are good, the armature is not worn out, and the output insulators are still good.
Also, there are several connections within the generator that can lose contact over time.
If the generator is up to snuff, it has to be either a bad ground or bad regulator.
One other thing to look for if you open up the generator. It is close quarters inside, if the insulation breaks down on a wire, it can be shorting itself out at times.
Also, there are several connections within the generator that can lose contact over time.
If the generator is up to snuff, it has to be either a bad ground or bad regulator.
One other thing to look for if you open up the generator. It is close quarters inside, if the insulation breaks down on a wire, it can be shorting itself out at times.
1959 JD 440ICD w/64 Power Angle Tilt Blade
1959 JD 440ICD w/63 Manual Angle Blade
1959 JD 440IC w/602 Manual Angle Blade
1959 JD 730D W SE (many options)
1950 JD M S w/M-20 Mower
1952 JD M W
1955 FORD 640 (burns the most fuel)
1959 JD 440ICD w/63 Manual Angle Blade
1959 JD 440IC w/602 Manual Angle Blade
1959 JD 730D W SE (many options)
1950 JD M S w/M-20 Mower
1952 JD M W
1955 FORD 640 (burns the most fuel)
- Stan Disbrow
- 350 crawler
- Posts: 2898
- Joined: Fri Jul 15, 2005 3:13 pm
- Location: Raleigh, NC
Hi,
There's a soft iron plate associated with each field coil in the generator. That's what you're polarizing (magnetically) when you go thru the procedure. They're supposed to provided enough magnetic field to produce an output voltage from the generator. That, in turn, closes the cut-out relay in the regulator, which then applies voltage to the field coils, boosting the mag field for high output.
If there is not enough magnetism in the plates you won't get enough voltage out of the generator to activate the coil in the cut-out relay.
So, you have to disconnect the power line from the generator and see if there's voltage at the output terminal with no load. If there is, then reattach the lead and measure again and see how much voltage you're losing. I'd reattach with an ammeter in the line as well (using a second meters) to see if I'm sinking current somewhere down the line.
It's also possible that the cut-out relay coil has shorted a winding or two, meaning that it will sink more current than normal and yet not produce enough mag field to close the contacts. This would be a faulty regulator, of course.
I had an issue just like this last summer. There was a piece of fuzz (looked like a weed seed of some sort) that had worked it's way into the regulator housing somehow. It was in between the cut-out relay contacts. That meant that the coil had to close with a tad more force than normal to make contact.
The symptom was that it would sometimes charge, sometimes not. When it would charge, it meant that I had to get the engine RPMs up high first. The faster the generator spins, the more voltage and current it will produce from the iron plates. Eventually, it was enough to force the cut-out relay contacts tighter and it would then 'make' and put current into the field coils. Plus, some vibration likely helped things along here.
I troubleshot it with the two-meter trick and also with a clip-cord between the battery and the field coil input terminal. That forced it to come on, but then the meters showed both a voltage and current change on the line to the cut-out, and I knew then that the issue was not in the generator, but in the regulator.
Which, was a PIA since one has to drain the coolant to remove the temp sensor from the head to then get the dash out far enough to get to the stupid regulator!
I'd have much rather worked on a bad generator!
Anyway, as I sit here reading your troubles, I wonder if you might not be fighting the same problem. You'd have a stronger mag field in the iron plates right after polarizing it. That might be enough to get it to work, but then the field will relax somewhat afterwards - so later on it doesn't work again.....
later!
Stan
There's a soft iron plate associated with each field coil in the generator. That's what you're polarizing (magnetically) when you go thru the procedure. They're supposed to provided enough magnetic field to produce an output voltage from the generator. That, in turn, closes the cut-out relay in the regulator, which then applies voltage to the field coils, boosting the mag field for high output.
If there is not enough magnetism in the plates you won't get enough voltage out of the generator to activate the coil in the cut-out relay.
So, you have to disconnect the power line from the generator and see if there's voltage at the output terminal with no load. If there is, then reattach the lead and measure again and see how much voltage you're losing. I'd reattach with an ammeter in the line as well (using a second meters) to see if I'm sinking current somewhere down the line.
It's also possible that the cut-out relay coil has shorted a winding or two, meaning that it will sink more current than normal and yet not produce enough mag field to close the contacts. This would be a faulty regulator, of course.
I had an issue just like this last summer. There was a piece of fuzz (looked like a weed seed of some sort) that had worked it's way into the regulator housing somehow. It was in between the cut-out relay contacts. That meant that the coil had to close with a tad more force than normal to make contact.
The symptom was that it would sometimes charge, sometimes not. When it would charge, it meant that I had to get the engine RPMs up high first. The faster the generator spins, the more voltage and current it will produce from the iron plates. Eventually, it was enough to force the cut-out relay contacts tighter and it would then 'make' and put current into the field coils. Plus, some vibration likely helped things along here.
I troubleshot it with the two-meter trick and also with a clip-cord between the battery and the field coil input terminal. That forced it to come on, but then the meters showed both a voltage and current change on the line to the cut-out, and I knew then that the issue was not in the generator, but in the regulator.
Which, was a PIA since one has to drain the coolant to remove the temp sensor from the head to then get the dash out far enough to get to the stupid regulator!
I'd have much rather worked on a bad generator!
Anyway, as I sit here reading your troubles, I wonder if you might not be fighting the same problem. You'd have a stronger mag field in the iron plates right after polarizing it. That might be enough to get it to work, but then the field will relax somewhat afterwards - so later on it doesn't work again.....
later!
Stan
There's No Such Thing As A Cheap Crawler!
Useta Have: '58 JD 420c 5-roller w/62 inside blade
Useta Have: '78 JD350C w/6310 outside blade
Useta Have: '68 JD350, '51 Terratrac GT-25
Have: 1950 M, 2005 x495, 2008 5103 (now known as 5045D)
Useta Have: '58 JD 420c 5-roller w/62 inside blade
Useta Have: '78 JD350C w/6310 outside blade
Useta Have: '68 JD350, '51 Terratrac GT-25
Have: 1950 M, 2005 x495, 2008 5103 (now known as 5045D)
I think I finally got to the bottom of this mystery. I had my dad look at the thing (that usually gets things fixed) and he showed me that when you ground the field terminal on the generator, the regulator is bypassed and the gauge should show full charge, which it wasn't. But if you rapped on the back of the generator with a hammer handle it would start to charge. So the new brushes were not contacting for some reason.
The generator has a neat little cover that you can remove to access the brushes without dismantling half the crawler. I checked them out, one looked fine, but on the other I discovered that some creature had crawled in there and attached a sticky mess of webbing to the brush.
My guess is that made enough resistance to prevent the brush from moving in as it wore, which eventually made the generator so spotty that the battery would not stay charged and there was not enough activity going on to maintain polarization.
When I started it after putting the brushes back in it began to charge immediately. It remains to be seen whether it will stay that way but at least now I know what to monkey with in the future.
However, the gauge still does this thing where if the throttle is wide open the needle bounces back and forth, I don't know what's doing that...
The generator has a neat little cover that you can remove to access the brushes without dismantling half the crawler. I checked them out, one looked fine, but on the other I discovered that some creature had crawled in there and attached a sticky mess of webbing to the brush.
My guess is that made enough resistance to prevent the brush from moving in as it wore, which eventually made the generator so spotty that the battery would not stay charged and there was not enough activity going on to maintain polarization.
When I started it after putting the brushes back in it began to charge immediately. It remains to be seen whether it will stay that way but at least now I know what to monkey with in the future.
However, the gauge still does this thing where if the throttle is wide open the needle bounces back and forth, I don't know what's doing that...
- Paul Buhler
- 350 crawler
- Posts: 991
- Joined: Wed May 21, 2008 6:25 pm
- Location: Killington, VT
polarizing generator
I too have a 6v new gen from this site that wont charge unless it is polarized, I have taken it apart and ensured the brushes were well seated and cleaned and tightened all electrical connections and now have a pushbutton across the cutout to give it a shot to start it generating???
Re: polarizing generator
Like my dad showed me, first connect a ground to the field side to bypass the regulator and be sure the generator is the problem. Also the generator does not charge till I rev the engine and after a couple seconds it kicks in. At idle there is only maybe 1 amp of charge.boler76 wrote:I too have a 6v new gen from this site that wont charge unless it is polarized, I have taken it apart and ensured the brushes were well seated and cleaned and tightened all electrical connections and now have a pushbutton across the cutout to give it a shot to start it generating???
So far it has been working ok, now I have a sunken float in the carb to contend with.
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