Generator Question.

[Rock10]

Our 1936 Series 40 has been converted to 12 volts. We recently found it wasn't charging. The Generator is from a 57 Chevy. I took it apart and found some missing old insulation on the field coils, but nothing that appeared to be shorted. When I checked the armature, all of the commutator segments show continuity. There is no resistance between them. According to videos on YT, there should be. Am I missing something? If the commutator is shorted, how would that happen to all of the segments? I see no damage on the part. The brushes were worn, but not totally gone and there isn't a groove where they run. Any thoughts?

Thanks.

[Jack Worstell]

Did you also change out the VR ?     The original generator was probably a three-brush and the 

57 Chevy   is a two-brush generator

I would guess the two generators take substantially VRs

Plus going from a 6V generator to a 12V generator calls for a VR change

 

Commutator segments show continuity ???  As measured to what reference ??

If the armature is out on the bench...I don't think adjacent segments should show continuity ???

 

Jack Worstell

[Rock10]

The VR was changed before we got it. Everything seemed to be fine until we noticed not charging a few weeks ago. The armature is out on the bench and each segment on the commutator shows continuity with every other segment. You are supposed to test them adjacent and 180 degrees apart. The videos show resistance between segments I have none. What would cause that?

Edited October 18, 2021 by Rock10 (see edit history)

[Rock10]

[Oldtech]

You would have very little resistance between segments and I don't think that is a valid test. Check from ground to the segments, there should be no reading. If it is grounded it wont work.  To test for short circuits in the armature you need a growler. If it passes the growler and is not grounded, it is good.  

[Bloo]

Without trying taking a generator apart to try it, i think its normal.

 

You should have continuity through the field, and open circuit from the field coil to the case (with it all apart).

 

On the armature make sure its open circuit from all the segments to the shaft. Then run it. Spin the engine up to a fast idle, fast enough that it would have been charging when it worked, and ground the FIELD terminal. It should charge like crazy. If it does, look elsewhere for the trouble.

 

If it doesn't, take the cover off the regulator, and do the same test again while pushing the cutout relay down manually. If it still won't charge then it is generator trouble for sure.

 

More in-depth tests of the armature or field require a growler. It probably is an armature problem if the field passes and it still wont work, but I might have some more ideas for kludgey tests if it fails to work with the field grounded.

 

 

Edited October 18, 2021 by Bloo (see edit history)

[Rock10]

None of the segments are shorted to the shaft, just each other.

[Rock10]

Where can I find a growler?

Tested on the car it would not put out any voltage with the field grounded.

[Bloo]

And you have continuity through the field coil?

[Oldtech]

Any electric motor shop will have one. So do a lot of hobbyists. The charge should be minimal to have one checked. 

 

In the electrical magic of a generator if any of the windings are shorted to another from being hot, physical damage, or whatever, it will not charge. it only takes one.  

You may have something else going on but getting the armature checked is always a good idea, 

[Rock10]

19 minutes ago, Bloo said:

And you have continuity through the field coil?

Yes

[Bloo]

By process of elimination it almost has to be the armature. It's still a goofy failure. I suggest getting the armature tested if you can.

 

[Rock10]

I'll check for a shop tomorrow. Thanks

 

[Frank DuVal]

16 hours ago, Rock10 said:

The brushes were worn, but not totally gone

 

Just how worn? How long are they? Do you have a new brush to see how worn the old ones are?🤔

[Jack Worstell]

Commutator sure doesn't look good.    Needs a good cleaning and maybe

turned down ( very lightly )  to eliminate any roughnesss

 

And clean the groves ( carefully ) between the segments

 

Do I think this will solve the charging problem ?

Probably not....but it's not hard to do

and if it were mine....I'd give it a shot

 

Jack Worstell

[Rock10]

9 hours ago, Frank DuVal said:

 

Just how worn? How long are they? Do you have a new brush to see how worn the old ones are?🤔

Still good material left. I've seen worse.

[Rock10]

5 hours ago, Jack Worstell said:

Commutator sure doesn't look good.    Needs a good cleaning and maybe

turned down ( very lightly )  to eliminate any roughnesss

 

And clean the groves ( carefully ) between the segments

 

Do I think this will solve the charging problem ?

Probably not....but it's not hard to do

and if it were mine....I'd give it a shot

 

Jack Worstell

I did a little cleaning between the segments and it looks like copper, not an insulator. 🤷‍♂️

[EmTee]

There are mica insulators between commutator segments.  If you have the commutator turned-down by an auto electric shop they will also cut the mica insulators to ensure they are below the copper surface the brushes ride on, allowing for wear.

[Jack Worstell]

If copper particles ( from wear of the copper commutator segments )

have filled in the groves between the commutator segments 

....then it seems to me that is the problem

 

I don't recall ever hearing of this condition getting to the point

of  "no charge"

 

Of course behind might be another problem of the armature

windings shorted to one another.

I guess this is what a "growler" test is supposed to detect

 

As EMTee have pointed out.....an auto electric shop

....if you can find one....might be able to correct the commentator issue

 

I see from your photos that the ID tag is still on the generator housing

If you have 1950s Delco Remy reference books....you can find

the correct armature replacement.  But maybe it's easier to just get

another generator

 

Jack Worstell