H generator brush question

Is there an easy way to to tell if the brushes are bad in my generator ?

The tractor quit charging yesterday. It would resume charging if it was at high rpm and I hit a bump. When I looked at it today, all the voltage regulator tests point to a bad generator.

Is there something else I should check ?

Thanks

Greg

Take off the band & have a peek.

The brushes must be long enough to have the spring assembly push them into contact with the armature. They must be free to move in the brush guise, and if too short will just barely make intermittent contact. Jim

Any idea how long the brushes have to be to be effective ?

I had a look, and they seem to click down onto the armature, but I can't tell what kind of contact they are making. Is there a stop that limits the travel of the brush holder ?

Greg

The armature will be discolored (blacky carbon) and there will either be no tension on the brush or it will stick in its holder and be imobile. New brushes are common, and cheap. Bew bushings/bearings should be put in at the same time. Jim

I cant give you any exact brush measurements, but related to Jims post if they are too short the springy brush push/hold downs will bottom out on the brush holder frames therefore NOT, as he points out, maintain strong constant brush hold down pressure.

Other problems may be the commutator is all gunked and black and/or oiled over which a good clean up and polish might cure

Other problems may be the spring assemblys on the brush hold/push downs are sticking, rusted or corroded and NOT maintaining good pressure which a good clean up and light lube and exercise may cure

Other problems are the commutator may need to have its seperator insulator segments undercut because they are too high causing brush bounce and poor contact

OF COURSE THE BRUSHES MAY JUST BE WORN DOWN TOO SHORT PLUS A TON OF OTHER POSSIBLE CAUSES OF NON CHARING UNRELATED TO THE BRUSHES

If you run my Par 5 VR by pass procedure (see my troubleshooting URL) yet she still fails to charge its more likely a genny itself versus a VR problem

John T
Troubleshooting

Generator brush size for generator # 1101355 is:

6.5 mm T
18.5 mm W
18 mm L.
(19 mm is about 3/4 inch)

Delco part number 820517.

Thanks Owen (and you other guys too),

That sounds about right. There is no number plate on this generator. I have 0.265" thick, 0.730" wide and between 12.1 and 13.8 mm long. The endplate fits over the commutator without spreading the brushes.

Do you know if those brushes have a hole in them for a mounting screw ?

My parts book show a wire lead attached to the brush. Upon disassembly, that is not what I have. The parts book also shows two numbers for the main brushes and the third brush, but the remains appear to be the same.

Thanks again

Greg

ps, I will clean up the commutator insulators, but I think I'll pass on the bearing and bushing. I want to do a litle disking and plant some peas and radishes tomorrow. I will order the parts and put 'em in at my next earliest convienience. Hopefully they don't have just the kids working the parts counter tomorrow...

The problem with the bushing is if it gets much wear on it it will allow the armature to touch the pole shoes and that will soon let all the magic smoke out of the generator.

Brush number 820517 has a slotted hole on one end and has no pig tail wire. I got that number out of my Delco book. It listed both main brushes and the third brush with the same number. Looking on line for the H generator parts listing I came up with # 1836664 for the main brushes and # 1880225 for the third brush. My electrical wholesaler crosses all of those numbers to the same brush.

Originally the third brush was softer. It doesn't have to carry as much current as the other two so it had more carbon and less copper. I still have a couple of the old third brushes on the shelf and you can tell them apart from the main brushes by their darker color.

The brushes with leads had the same differences but again the third brush has been discontinued and the main brush is used instead. They are also the same brushes as used in the two brush generators. Part numbers for those brushes are 1906940 or 1850078 for the third brush and 1906984 or 1880998 for the main brushes.

It looks like brushes that are less than 1/2" long are too short.

Thanks for the help guys

Greg