Not charging. I think??

[andrewLL 15]

I'm hoping that someone may be able to point me in the right direction here.  I recently restored a Raider 12 and ran it around the garden briefly before taking it to bits and then out to France where I put it back together again.  That was this time last year and I cut about half an acre of brambles and bracken.  It was then used again in March and June with no problems, but recently having used it again, it would not start after a run.  The starter was not turning and no click from the solenoid, but it started first go with jump leads onto the car and then stopped as soon as they were removed.  I charged the battery which is only a year old and it worked fine.  I guess it's not charging and that I have just been running it from the battery all the time.

What I have remembered from when I stripped the machine down was that there was a question about this, but when it all went back together and ran ok I forgot all about it.  I did measure the resistance across the alternator coils at the time and there was continuity but I can't remember the resistance reading.  When the engine is running at idle speed the ammeter oscillates quickly from positive to negative but this stops when the engine revs are increased and settles down to a small discharge current, about the thickness of the needle.  

Any suggestions what this could be?  The problem I have is that I am not going back to France for a few months and would like to take the necessary parts over to fix it.

Also I have just bought a tiller to go on the back and will need some advice on the lift mechanism, but will put this as a separate post.

Any thoughts would be appreciated.
Andrew

  

[953 nut 51,675]

            You do nice work!  Since this is a new restoration I presume all of the electrical connections are free of corrosion and made up tightly. You may have a bad voltage regulator or it could be that it isn't getting a proper ground through all of that new paint. Half of all electrical circuits are comprised of grounds and they need to be good also.

[WNYPCRepair 1,875]

Sorry for the off topic post, but what year is that MGB? I miss mine....  

[KC9KAS 4,741]

You need to measure AC voltage on the 2 wires coming from the alternator (behind the flywheel). This entire procedure is done with the engine running. This voltage should be 24 to 28 VAC at 1/2 or more throttle. If this is good, measure the voltage from the regulator B+ terminal and it should read 12.8-14.4 volts DC. As stated earlier, the regulator MUST have a good ground. If questionable, attach a "jumper" from the battery negative (-) post to the regulator for testing purposes.

You need 24 to 28 volts AC INTO the regulator, and 12.8-14.4 volts DC OUT of the regulator.

[gwest_ca-(File Mod) 10,496]

One more test you can make.

Turn the ignition key to the RUN position with the engine not running.
Measure the voltage across the battery posts and record.
Move the red test lead to the regulator DC+ output terminal. You should have the same reading.

If not the path the charge current takes to get to the battery through the ignition switch is not complete.

Garry

 

[andrewLL 15]

The answer to the question about my MG is that it is a 1980 model.  I'm sure someone will notice that the bumpers are not the standard black rubber things that had to be added to keep the U.S. regulators happy.  Unfortunately changing the bumpers is not quite as simple as a straight swap.  The front wings also had to be changed to ones with holes for the indicators and side lights, not that that was a problem as I replaced all the external panels except the bonnet and boot lid.  The ride height was also raised on the rubber bumper models and that has been corrected with new springs front and rear.

Thanks for all the helpful replies about my charging problem.

Andrew