QuestionQUESTION: I have a Lucas 22744B C40 generator that came from a 1961 MGA that has set for years. I atempted to bench check it with a dc voltmeter run from the D (large spade) terminal and grounded to the casing, then turning the pulley with a drill - got nothing. My research found something that said the magnetic field can be lost when setting inactive. Request your thoughts on the validity of this, and what must I do to diagnose the generator.
I just read you answers about a 67 MGB system and understand I would do a full field test by:
1) making a jumper that connects the D and F terminals on the generator
2) I want to set the gen up for a negative ground in my rebuild so I should connect the positive term of the battery to the D term of the gen and the neg battery term to the gen casing.
3) turn the armature with the drill to check voltage output
Am I on the right track?
So, First I need to address the lost field issue then run the above test?
Thanks in advance
Bruce
ANSWER: Hi Bruce,
Yes you are doing it correctly. When you first connect it up (in the same polarity as you want it in the car), Before you connect it up to your drill motor, just connect it to a strong battery and watch the pulley. It should start turning like a slow electric motor and in the SAME direction as the engine turns. Let it run that way for a minute or two. If it just moves a little but don't turn, give it a hand spin to see if it will continue to turn. I have run across a few that would only make a small effort to turn like a motor but still worked ok. The important thing is to leave it connected to the battery for a few seconds at a time if it don't turn by it self and to leave it connected for a couple of minutes if it will run like a slow electric motor. That will polarize the generator.
Don't forget to switch all the items in the car as I had stated. You can also read my tech tip on my website on the subject. (http://mg-tri-jag.net/tech1.htm) Good luck, let me know how it turns out.
Howard
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QUESTION: Howard,
No Luck. I tried running the generator with the D - F jumper on, battery negative to casing and battery positive to the D. I didn't see the armature move or run.
With nothing hooked up, when I spin the armature by hand it rotates freely and continues to spin with little resistance. When hooked up, I helping it to turn as you suggested but it still did not run. I did however notice that the armature no longer would spin feely, stopping as soon as I quit trying to spin the armature. I did not attempt to spin the generator with the drill in this configuration.
Other possibly pertinent information:
- Battery I used for this all was at 12.4 on the voltmeter.
- Removed the jumper and put the battery positive to the field (F) and neg to the casing for about 5 sec (3 times). Got nothing on the voltmeter while spinning the generator with the drill.
- I haven't disassembled anything yet but the brushes appear to be in contact with the armature.
Should I assume it's time for a new generator or are there some other things to try.
Bruce
No luck.
AnswerI agree, it is either rebuild time or new. Before that I would take it apart and do a few things. First clean the armature with Emory cloth and check with an ohm meter to see if the commutator has any connection to the shaft and check to see if the armature or fields look or smell burned. Also that the brushes are long enough to press on the commutator. Run 12v through the fields to see if they both are magnetic with power. Any local generator/ alternator rebuild shop can check the armature for you as far as the windings on a thing called a growler.
Howard
