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Yesterday my starter stopped working - M35G, early inertia type. Today I removed it and tested the connection from the solenoid (OK) and the starter on the ground (sparks and not working).

Took it appart expecting to find evidences of a short circuit, but didn't find anything. No black marks or signs of unusual wear/something wrong.

After a couple of careful re-assemblies having always the same result, I bought self welding tape and isolated everything POSITIVE that could be touching the case/body (earth), top cover and big clamp. A few assemblies later I was still having the same results. I checked and rechecked with the help of a lamp (my multimeter died last week) every part on the case and:

- Body/case: No current is passing to the body or field plates (100% sure!). Current only flows on the thick winding 'wires', POSITIVE brushes and respective holders properly isolated from the top cover.
- Armature: No current is passing from the commutator to the shaft/body. All commutator 'lines' are connected.

But:
- If I connect the battery positive terminal to the starter threaded pin and earth one end of the lamp, it turns on if I use the other end on the case.



After a few careful checks, I noticed that this only happens when the positive brushes touch the commutator (the armature is not fouling anywhere, I'm sure of that, and the threaded pin has the plastic isolator). I believe that my lamp should NOT be on and this is what's causing my short circuit. Can anyone confirm my thoughts?

Oh, and I tested another worn starter I have and the results are exactly the same, even after a few parts swapped to track down (inconclusively) the problem. I don't think I'm doing it wrong, but I must be missing something. If you put 12V on the starter and earth the case, it should work, right? Mines are just sparks!

Can anyone help? I'm running out of ideas and a little lost.

Now that I think of it:

- Positive brushes have 12V
- Commutator flows well
- Earthed brushes are making the bridge to the case

My lamp should be ON. It's the basics to put an armature spinning, current and earth on the commutator.

So why my starter doesn't spin and I only get big sparks when I try to test it? My brain is melting

These sort of things can be hard to sort over the web!

However, I have had a few where the insulator on the stud that the main lead connects to, wear through, thereby putting a dead short across the starter. It's just a bakerlite sleeve.

Another problem I've come across is the front Bush (as in bearing) wears so much the the starter is said to Pole Out, that's where the armature jams against the field coils. They usually spin over by hand OK, but when energised, the magnetisim created causes the Poling Out.

Hi Spider,

thanks for the reply, you were right! I had my eyes so open that I wasn't actually seeing it, it was the stud.



These final adjustments on my car before its first (ever) MOT have been painful! Last Saturday a tappet cover gasket failed with the heat... oil everywhere. Then I found another set of gaskets in the garage (older stock I suppose) which are smaller and are fitted in tension, not like the new/bigger ones which are prone to escape if you tight them more than... by hand? I assume the bigger gaskets are to be used with the later covers with the lip to hold them. I wonder where I got the other set from!

richardo, good result, thanks for letting us know. It was only a wild experienced guess on my part!