Starter communicator repair

[36Limited]

I am building a backup starter. The starter works good as long as I dont not crank it to much. I then have to sand commutator and brushes and it works again. So there is a gap between commutator segments. The material between starter commutator has deteriated. I read a substance mica was used before. Also different polymers were used as well as thin sheets of plastic. Does anyone recommend a polymer to fill in the spaces between the commutator segments? This is where the starter brushes contact. I would probably brush on in between segments then sand smooth when dry.

Thanks everyone for your input.

Edited June 5, 2012 by 36Limited
spelling (see edit history)

[Restorer32]

I believe you mean "commutator".

[oldford]

The mica between the segments of the commutator are simply insulators. If the mica is missing, it implies that the armature has suffered from excess heat and is most likely warped or has internal damage. I would suggest that you try to find another armature rather than repair this one. You did not mention the model of car you are working on, but unless it is so rare that this is your only option, I'd find another starter...

Frank

[Bhigdog]

The mica is supposed to be undercut and below the segments. What you see may be normal. Slathering some kind of goo on the commutator may well ruin it or make a lot of extra work trying to undo whatever you did. Sanding the commutator is not a good idea as the sand grits can get lodged in the soft copper. Depending on what you used the grit may also be conductive. I would recommend you take the armature to a motor shop and have the commutator turned and undercut as needed. It doesn't cost much...........Bob

[startergenrebuilder]

Bob is correct. The mica between the commutator bars should be undercut. Although, if you are getting sparking/arcing so bad that you need to polish it that often, there is something wrong. At the very least your armature comm needs to be machined true, and re-undercut as well as tested/evaluated for shorts or opens. Feel free to contact me with any further questions.

Jason

[Rusty_OToole]

I agree heartilly with the advice to take the starter to a good rebuilder.

The mica insulation does need to be undercut or cut away slightly. You can do this using a broken fine tooth hacksaw blade that has been ground down to a suitable thickness.

The reason your starter is giving trouble is, the brushes are riding on the mica insulation and not making good contact.

There could be other problems. A good auto electric shop will rebuild your starter good as new.