H Starter short circuit

I took it apart, and although I'm no expert, it seems that the issue is either worn brushes (they look pretty worn, but SEEM to be making contact), or the 'arm' that connects from the starter's post to the windings.

So 1) would worn brushes cause a popping/short circuit? 2) What should the resistance be between the post and the starter housing when assembled? (I'm getting around 4 ohms, which seems wrong, but I'm not sure). 3) How do the windings connect to the post? What I have looks like a total hack. The 2 'arms' from the windings seem to just lie in the slot of the post. That can't be the way it's supposed to be. I think the one arm may be touching the commutator, because it's pretty bent up and looks a little 'scorched'. I tried to bend it back to where it goes around the housing nicely, but it's a little short to reach the post when I do that, and it still seems to have the short.

Any initial ideas? Anyone have any pictures of a disassembed, good starter?

Sometimes if the bushings are worn enough the armature can drag on the field housings and cause enough heat to melt the insulation and cause an internal short in the windings. If you have a growler (older device for testing internal shorts in armatures) test it (or take it to a place that has one like an automotive machine shop) to make sure it isn’t internally shorted. Check the brush connections. Two of the brushes should have a braided wire to the housing end cap, and the other two should be connected to the field windings (taken out from the access holes behind the narrow band on teh commutator end of the starter) which connect to the post on the field housing that the battery cable connects to.

While the starter is completely disassembled if you have current flow from any copper part (including brushes) to a steel part (except brush holders), this is where the short is at. Once the starter is assembled, then there will be conductivity, since that is how electric motors work.

If you don’t find a short after the above tests, I would recommend replacing the bushings and the brushes get a good brush arm and put it back together and bench test it. You won’t have much in it.

Good luck. e-mail me if you have questions.

But when it's assembled, I'm still worried about how the winding's arm is routed, and how it connects to the post. It seems like that's the only suspicious part now, and could explain why it seems fine when disassembled, but it shorts out when assembled. How much room is there between the arm and the housing, and between the arm and the commutator (steel part)? I think it must be touching one of those two right now, and I can't seem to get it right.

And how does the arm connect to the post? I just don't see how there was ever a solid connection there, although I don't think that's my immediate problem.

Thanks

This is from memory, but I believe that two brush arms share a pivot pin and mounting bracket on the cover of the starter. Behind each arm is a spring that holds the brush firmly against the commutator. There isn’t a lot of clearance between the brush arm and the commutator or the field housing of the starter, since the movement required for the brush arm is relatively minimal. The brush arm should not touch anything except the brush, the pivot pin and the spring that holds the brush against the commutator (armature). If the brush arm touches the commutator, a new brush may be all that is needed to correct this. The brushes normally extend about 3/16 of an inch between the arm and commutator.

The connection of the “grounding” brush is straight forward, braided wire to the end cap of the starter. The “hot” one may or may not be so straight forward. When you disassembled the starter, you should have had to remove two screws from wire leads or possibly a flat copper piece in order to get the end cap off. This is where the “hot” brushes connect. This may be a direct connection to the terminal on the starter or may be a “tap” off the field windings; I’m not positive on yours as starters can be made either way.

The power flow is from the terminal on the outside of the starter where the battery cable connects, through the field windings on the outside of the housing to two of the brushes (hot) through the commutator to the windings in the armature, out through the two grounded brushes. That being said, the connection of the “hot” brushes is actually made to the field windings or directly to the terminal on the starter. I have seen starters that have had an oversized flat screwdriver slot in the bottom of the terminal that the battery cable connects to and the field and brush leads were soldered into this grove. Possibly on yours, it may have gotten hot enough to melt this solder out and that is why you are not seeing where the connection is at.

Hope this helps, fire back if you have more questions…

I explained part of it wrong (I knew I would). The 'arm' I was talking about is the thick metal 'lead' from the windings to the external post. The longer one is all scorched, and I was thinking it was either making contact with the housing, or with the end of the commutator. Unfortunately you can't really tell when it's apart, and there's no way to get to it when it's assembled.

It looks like the solder from the 'lead' is long gone if it was on there (it's the large screwdriver type post). I'm surprised this isn't more of an issue, as it seems like the routing of the lead is pretty error prone, and it doesn't seem as those there is alot of room for error/movement.

I'll check the brush arms though also, as that's a good idea. Maybe they were touching the copper.

Thanks

Glad I could be of help. Good luck with your starter.