Curti Posted March 6, 2014 Share Posted March 6, 2014 I have an Auto-Lite generator that motors too fast. The single output wire to the cutout has direct short to the frame. Many years ago I had the same problem, but I cannot remember what the diagnosis was. Link to comment Share on other sites More sharing options...
oldford Posted March 6, 2014 Share Posted March 6, 2014 Well, how did you check for a short? With the brushes touching the commutator, you will have a dead short. Place a piece of paper under each brush to see if the short goes away. if so, That's your problem.... Seriously, there are many things that can cause it... Brushes touching the frame, wire from the brush loose, insulating bushing at the post is gone... so on...Frank Link to comment Share on other sites More sharing options...
Curti Posted March 7, 2014 Author Share Posted March 7, 2014 With the brushes touching the commutator, you will have a dead short. Well, I didn't think of that! This is a body off restoration that I am in the process of sorting. I put the generator on the car, started it, and it didn't deflect the amp meter at all. The possibility exists that the amp gauge is defective so I put another amp gauge in line and proved that the generator was not charging. I removed the generator and motored it. Not only did it motor, but it spins at 2-3 times the RPM I would expect it to. I am better at trouble shooting mechanical that electrical. Link to comment Share on other sites More sharing options...
Dan Caswell Posted March 8, 2014 Share Posted March 8, 2014 You will probably have to replace the armature now; you have more than likely magnetized it. Generators are ruined very easy by spinning them with current - they are not designed for this. You are only supposed to "flash" current to them to polarize them. I have seen many people do what you did; & it results in complete rebuild of the generator afterwards. Sorry.Dan Caswell, Minot, ND Link to comment Share on other sites More sharing options...
Curti Posted March 8, 2014 Author Share Posted March 8, 2014 Wow, When I was young, and went to the salvage yards the 'test' was to see if the generator would motor. I have tested armatures on a growler with a hacksaw blade that is one heck of a magnetic field. Link to comment Share on other sites More sharing options...
startergenrebuilder Posted March 9, 2014 Share Posted March 9, 2014 Hopefully I can clear some things up. First off, you will not damage the generator by motoring it as long as it's not done for a long period of time. It is a very common quick test to see if generator functions. As a matter of fact, most rebuilders will motor a generator quickly to test and see direction before testing for output. Second, a generator can not really motor too fast. If you motor a generator without full fielding it, it will motor faster than if the field is grounded (full-fielded). Let me know if I can help you or further explain anything else. -Jason Link to comment Share on other sites More sharing options...
Graham Man Posted March 12, 2014 Share Posted March 12, 2014 Did you polarize the generator? If not, it will not have any output. Lots of old tractor sights have the method to polarize it. Link to comment Share on other sites More sharing options...
Curti Posted March 12, 2014 Author Share Posted March 12, 2014 I did polarize it. Then I removed the cutout, and tried it again, without any luck. That is when I motored it and the RPM was twice what I would expect it to be. I will be tearing the gen down this afternoon and will be looking for a grounded field coil. Link to comment Share on other sites More sharing options...
Curti Posted March 13, 2014 Author Share Posted March 13, 2014 Ok, I removed the commutator end plate brushes etc. I found the field wire that cuts across was grounding to one of the long screws that tie the end plates together. There is supposed to be a stiff paper barrier there that was missing. I put it back together and tested it. It motors slow like it is supposed to BUT it turns CCW in stead of CW from the drive end. I polarized it + ground - to the single wire (field) that goes to the cutout. It still runs CCW. Maybe I should have polarized it prior to motoring it. Link to comment Share on other sites More sharing options...
startergenrebuilder Posted March 13, 2014 Share Posted March 13, 2014 No need to polarize it when motoring. Actually when you motor the generator, you are polarizing it.-Jason Link to comment Share on other sites More sharing options...
Curti Posted March 14, 2014 Author Share Posted March 14, 2014 I got it , the gen now motors at the desired slow speed and turns clockwise as it should. I had a wire swapped around Thanks for the help fellas, particularly Jason! Link to comment Share on other sites More sharing options...
c49er Posted March 21, 2014 Share Posted March 21, 2014 How do you properly motor a generator? Link to comment Share on other sites More sharing options...
Curti Posted March 21, 2014 Author Share Posted March 21, 2014 My cars are + ground. So I get a 6V battery , attach the + cable to a ground and touch the - cable to the armature wire coming out of the generator that attaches to the bottom of the cutout . Later generators have a FLD stud and a ARM stud in this case touch the ARM stud. Link to comment Share on other sites More sharing options...
c49er Posted March 23, 2014 Share Posted March 23, 2014 Thanks!!! Link to comment Share on other sites More sharing options...
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