I have a T starter that failed. After a little testing I determined that the stator coil was shorting to the case so I disassembled the whole thing and installed a brand new stator winding from one of the T vendors. It took some effort to get the pole pieces so they didn't touch the rotor, but I'm sure the are now correct.
It still failed, no shorts but runs very slow. So I tried a new rotor and get exactly the same results. I have checked the brush holders two are grounded the other two isolated from the case.
I am beginning to suspect the new stator coils are bad, has anyone had any bad experiences (or success) with new coils?
I had a similar problem with the starter in my swather this summer. It turned out to be corrosion around the ground brush holder rivet. PK
Hook a voltmeter to the starter connection as well as directly to the starter case. Then try again. You should have right about 6 volts. I've heard of enough poor battery and cable connections
Right now the bad starter is my test fixture which has prestine cables and lots of current available.
Pat may be on to something as I did notice that after the failed test, the end cover was warm.....
Brushplate failures are very common in Model T starting motors. You cannot see the back side of the brushplate so the brush plate MUST be removed from the cap and carefully inspected/tested for faults. I ALWAYS remove and completely rebuild the brushpate and reinstall with copper rivets using a proper aircraft rivet gun and buck.